ORCID Profile
0000-0001-6691-1438
Current Organisations
University of Sydney
,
University of New South Wales
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Physical Chemistry (Incl. Structural) | Structural Chemistry and Spectroscopy | Chemical Spectroscopy | Optical Properties of Materials | Macromolecular and Materials Chemistry | Photodetectors, Optical Sensors and Solar Cells | Physical Chemistry not elsewhere classified | Organic Semiconductors | Structural Chemistry | Physical Chemistry of Materials | Nanotechnology | Condensed Matter Physics | Chemical Thermodynamics and Energetics | Quantum Chemistry | Nanochemistry and Supramolecular Chemistry | Electrical and Electronic Engineering | Other Instrumental Methods | Alloy Materials | Proteins and Peptides | Theory and Design of Materials | Transport Properties and Non-Equilibrium Processes | Instruments And Techniques | Physical Chemistry Not Elsewhere Classified | Nanotechnology | Materials Engineering | Astronomy And Astrophysics | Electronic and Magnetic Properties of Condensed Matter; Superconductivity | Nonlinear Optics and Spectroscopy | Molecular and Organic Electronics | Condensed Matter Physics—Electronic And Magnetic Properties; | Galactic Astronomy
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Solar-Photovoltaic Energy | Expanding Knowledge in the Physical Sciences | Chemical sciences | Physical sciences | Renewable Energy not elsewhere classified | Other | Solar-photoelectric | Medical instrumentation | Integrated circuits and devices | Hydrogen Production from Renewable Energy | Expanding Knowledge in the Biological Sciences |
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Publications
The structure and luminescence properties of europium(iii) triflate doped self-assembled pyromellitamide gels
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1NJ20085B
Excitation and Emission Spectra of Jet-Cooled Naphthylmethyl Radicals
Publisher: American Chemical Society (ACS)
Date: 16-06-2011
DOI: 10.1021/JP203638H
Abstract: Gas phase excitation and emission spectra of three naphthylmethyl radical chromophores are presented. These resonance-stabilized species, 1-naphthylmethyl, 2-naphthylmethyl, and α-acenaphthenyl, each possessing an sp(2) carbon adjacent to a naphthalene moiety, are studied by resonant two-color two-photon ionization, laser induced fluorescence, and dispersed fluorescence spectroscopy. Identification of the radicals is made through a combination of dispersed fluorescence and density functional theory calculations. All three species possess spectra in the 580 nm region. The possible relevance to unidentified spectroscopic features such as the diffuse interstellar bands and emission from the Red Rectangle nebula is discussed.
Interconversion of Methyltropyl and Xylyl Radicals: A Pathway Unavailable to the Benzyl–Tropyl Rearrangement
Publisher: American Chemical Society (ACS)
Date: 29-01-2018
Abstract: The products of an electrical discharge containing toluene are interrogated using resonance-enhanced multiphoton ionization and laser-induced fluorescence spectroscopies. A previously unreported electronic spectrum recorded at m/z = 105, with a putative origin band at 26053 cm
Calculating curly arrows from ab initio wavefunctions
Publisher: Springer Science and Business Media LLC
Date: 12-04-2018
DOI: 10.1038/S41467-018-03860-2
Abstract: Despite being at the heart of chemical thought, the curly arrow notation of reaction mechanisms has been treated with suspicion—the connection with rigorous molecular quantum mechanics being unclear. The connection requires a view of the wavefunction that goes beyond molecular orbitals and rests on the most fundamental property of electrons. The antisymmetry of electronic wavefunctions requires that an N -electron wavefunction repeat itself in 3 N dimensions, thus exhibiting tiles. Inspection of wavefunction tiles permits insight into structure and mechanism. Here, we demonstrate that analysis of the wavefunction tile along a reaction coordinate reveals the electron movements depicted by the curly arrow notation for several reactions. The Diels–Alder reaction is revealed to involve the separation and counter propagation of electron spins. This unprecedented method of extracting the movements of electrons during a chemical reaction is a breakthrough in connecting traditional depictions of chemical mechanism with state-of-the-art quantum chemical calculations.
Laboratory Spectroscopy of PAHs
Publisher: Cambridge University Press (CUP)
Date: 05-2013
DOI: 10.1017/S1743921313015950
Abstract: Spectroscopic investigations of PAHs have been conducted for many years, commencing with solid and solution studies and more recently including gas phase characterisation of a broad range of different species. Through the development of new, efficient methods of production and more sensitive spectroscopic techniques, fresh data are becoming available for not only neutral species, but also for radicals, ions and clusters.
Tunable self-assembly of triazole-linked porphyrin-polymer conjugates
Publisher: Wiley
Date: 12-08-2013
Abstract: The convergence of supramolecular chemistry and polymer science offers many powerful approaches for building functional nanostructures with well-defined dynamic behaviour. Herein we report the efficient "click" synthesis and self-assembly of AB2 - and AB4 -type multitopic porphyrin-polymer conjugates (PPCs). PPCs were prepared using the copper(I)-catalysed azide-alkyne cycloaddition (CuAAC) reaction, and consisted of linear polystyrene, poly(butyl acrylate), or poly(tert-butyl acrylate) arms attached to a zinc(II) porphyrin core via triazole linkages. We exploit the presence of the triazole groups obtained from CuAAC coupling to direct the self-assembly of the PPCs into short oligomers (2-6 units in length) via intermolecular porphyrinatozinc-triazole coordination. By altering the length and grafting density of the polymer arms, we demonstrate that the association constant of the porphyrinatozinc-triazole complex can be systematically tuned over two orders of magnitude. Self-assembly of the PPCs also resulted in a 6 K increase in the glass transition temperature of the bulk material compared to a non-assembling PPC. The modular synthesis and tunable self-assembly of the triazole-linked PPCs thus represents a powerful supramolecular platform for building functional nanostructured materials.
Spectroscopic Observation of the Resonance-Stabilized 1-Phenylpropargyl Radical
Publisher: American Chemical Society (ACS)
Date: 15-02-2008
DOI: 10.1021/JA078342T
Abstract: The gas-phase laser-induced fluorescence (LIF) spectrum of a 1-phenylpropargyl radical has been identified in the region 20,800-22,000 cm(-1) in a free jet. The radical was produced from discharges of hydrocarbons including benzene. Disregarding C2, C3, and CH, this radical appears as the most strongly fluorescing product in a visible wavelength two-dimensional fluorescence excitation-emission spectrum of a jet-cooled benzene discharge. The structure of the carrier was elucidated by measurement of a matching resonant two-color two-photon ionization spectrum at m/z = 115 and density functional theory. The assignment was proven conclusively by observation of the same excitation spectrum from a low-current discharge of 3-phenyl-1-propyne. The apparent great abundance of the 1-phenylpropargyl radical in discharges of benzene and, more importantly, 1-hexyne may further underpin the proposed importance of the propargyl radical in the formation of complex hydrocarbons in combustion and circumstellar environments.
Limitations and design considerations for donor-acceptor systems in luminescent solar concentrators: The effect of coupling-induced red-edge absorption
Publisher: IOP Publishing
Date: 12-05-2016
Singlet Fission in Concentrated TIPS-Pentacene Solutions: The Role of Excimers and Aggregates
Publisher: American Chemical Society (ACS)
Date: 16-08-2021
DOI: 10.1021/JACS.1C05767
Development of tethered dual catalysts: synergy between photo- and transition metal catalysts for enhanced catalysis
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0SC02703K
Abstract: A series of tethered dual catalysts were developed, with catalytic investigations demonstrating that tethering enhances photocatalysis and thermally activated Ir catalysis. In addition, sequential and switchable catalytic reactivity was achieved.
Laser-Induced Fluorescence Spectrum of 3-Vinyl-1H-indene
Publisher: American Chemical Society (ACS)
Date: 11-04-2007
DOI: 10.1021/JP068844D
Abstract: The laser-induced fluorescence spectrum of 3-vinyl-1H-indene was recorded between 33,000 and 33,800 cm(-1). An origin band was observed at 33,455 cm(-1) along with several low-frequency modes. With the aid of density functional theory and configuration interaction calculations, the electronic transition was assigned as S1 <-- S0 and the short progression in an 80 cm(-1) mode was identified as a vinyl group torsion. Theoretical, spectroscopic, and thermochemical considerations suggest that the 3-vinyl-1H-indene spectrum results from excitation from both conformational isomers with the vinyl and indene double bonds in trans and cis arrangements. The results are discussed in the context of the identification of species arising from the discharge of benzene in argon.
Role of Surface Capping Molecule Polarity on the Optical Properties of Solution Synthesized Germanium Nanocrystals
Publisher: American Chemical Society (ACS)
Date: 07-06-2017
DOI: 10.1021/ACS.LANGMUIR.7B01028
Abstract: The role surface capping molecules play in dictating the optical properties of semiconductor nanocrystals (NCs) is becoming increasingly evident. In this paper the role of surface capping molecule polarity on the optical properties of germanium NCs (Ge NCs) is explored. Capping molecules are split into two groups: nonpolar and polar. The NCs are fully characterized structurally and optically to establish the link between observed optical properties and surface capping molecules. Ge NC optical properties altered by surface capping molecule polarity include emission maximum, emission lifetime, quantum yield, and Stokes shift. For Ge NCs, this work also allows rational tuning of their optical properties through changes to surface capping molecule polarity, leading to improvements in emerging Ge based bioimaging and optoelectronic devices.
Intramolecular Versus Intermolecular Triplet Fusion in Multichromophoric Photochemical Upconversion
Publisher: American Chemical Society (ACS)
Date: 30-07-2019
Extended hot carrier lifetimes observed in bulk In0.265±0.02Ga0.735N under high-density photoexcitation
Publisher: AIP Publishing
Date: 28-03-2016
DOI: 10.1063/1.4945594
Abstract: We have investigated the ultrafast carrier dynamics in a 1 μm bulk In0.265Ga0.735N thin film grown using energetic neutral atom-beam lithography/epitaxy molecular beam epitaxy. Cathodoluminescence and X-ray diffraction experiments are used to observe the existence of indium-rich domains in the s le. These domains give rise to a second carrier population and bi-exponential carrier cooling is observed with characteristic lifetimes of 1.6 and 14 ps at a carrier density of 1.3 × 1016 cm−3. A combination of band-filling, screening, and hot-phonon effects gives rise to a two-fold enhanced mono-exponential cooling rate of 28 ps at a carrier density of 8.4 × 1018 cm−3. This is the longest carrier thermalization time observed in bulk InGaN alloys to date.
Spectroscopic Identification of the Resonance-Stabilized cis- and trans-1-Vinylpropargyl Radicals
Publisher: American Chemical Society (ACS)
Date: 28-08-2009
DOI: 10.1021/JA904521C
Abstract: The cis-1-vinylpropargyl (cis-1VPR, cis-pent-4-en-1-yn-3-yl) and trans-1-vinylpropargyl (trans-1VPR, trans-pent-4-en-1-yn-3-yl) radicals, produced in a supersonically cooled hydrocarbon discharge, have been identified by a synergy of 2-dimensional fluorescence and ionization spectroscopies, revealing their electronic origin transitions at 21,232 and 21,645 cm(-1) respectively. These assignments are supported by an excellent agreement between calculated ground state frequencies of cis-1VPR and trans-1VPR with those obtained by dispersed fluorescence spectroscopy. In addition, high-resolution rotational contours of the two bands are well simulated using calculated X- and A-state trans-1VPR and cis-1VPR rotational constants. Finally, computed origin transition energies of these two isomers are within several hundred wavenumbers of the observed band positions. With the 1-phenylpropargyl radical, the 1VPR isomers are the second 1-substituted propargyl species to have been observed abundantly from a hydrocarbon discharge, while no 3-substituted analogue has been positively identified. This is likely due to the greater resonance stabilization energy of the 1-substituted species, arising from concerted delocalization of the unpaired electron over the vinyl and propargyl moieties.
Electronic Spectroscopy of PAHs
Publisher: EDP Sciences
Date: 2011
DOI: 10.1051/EAS/1146037
On the Electronic Properties of Dehydrogenated Polycyclic Aromatic Hydrocarbons
Publisher: American Chemical Society (ACS)
Date: 15-04-2006
DOI: 10.1021/JP057441V
Abstract: The electronic excited-state properties of a series of dehydrogenated polycyclic aromatic hydrocarbons from phenyl through to decacyl are reported. The radicals were investigated by use of time-dependent density functional theory in conjunction with the B3LYP functional. The pi and n orbitals were seen to converge in energy as the system increased in size, yet all radicals were found to have A' ground states. In addition to the study of the electronic state symmetries, the excited-state transitions and oscillator strengths were investigated with the resulting transitions found within the visible region of the spectrum, placing these radicals in the large group of candidate carriers of the diffuse interstellar bands.
Inter-ligand energy transfer in dye chromophores attached to high bandgap SiO2 nanoparticles
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CC03412A
Abstract: Simple artificial light harvesting networks can be created by the covalent attachment of organic chromophores to silicon dioxide nanoparticles.
Hot carrier dynamics in InGaAs/GaAsP quantum well solar cells
Publisher: IEEE
Date: 06-2011
Spectroscopy of the free phenalenyl radical
Publisher: American Chemical Society (ACS)
Date: 30-08-2011
DOI: 10.1021/JA206322N
Abstract: After benzene and naphthalene, the smallest polycyclic aromatic hydrocarbon bearing six-membered rings is the threefold-symmetric phenalenyl radical. Despite the fact that it is so fundamental, its electronic spectroscopy has not been rigorously scrutinized, in spite of growing interest in graphene fragments for molecular electronic applications. Here we used complementary laser spectroscopic techniques to probe the jet-cooled phenalenyl radical in vacuo. Its spectrum reveals the interplay between four electronic states that exhibit Jahn-Teller and pseudo-Jahn-Teller vibronic coupling. The coupling mechanism has been elucidated by the application of various ab initio quantum-chemical techniques.
The Optical Spectrum of a Large Isolated Polycyclic Aromatic Hydrocarbon: Hexa- peri -hexabenzocoronene, C 42
Publisher: American Astronomical Society
Date: 17-06-2008
DOI: 10.1086/590207
Kinetic analysis of photochemical upconversion by triplet-triplet annihilation: Beyond any spin statistical limit
Publisher: American Chemical Society (ACS)
Date: 25-05-2010
DOI: 10.1021/JZ100566U
Visualizing the 30-Dimensional Antisymmetrized Electronic Structure of Water: The Emergence of Lone Pairs
Publisher: American Chemical Society (ACS)
Date: 09-01-2020
DOI: 10.1021/ACS.JPCLETT.9B03528
Abstract: The electronic structure of water is typically thought of as exhibiting lone pairs of electrons, described by some as "rabbit ears". This is not the universal view, and it does not mesh with an interpretation based on the one-electron wave functions that emerge from molecular orbital theory. Here, we show, by analyzing the 30-dimensional antisymmetrized wave function (Slater determinant) rather than the Hartree product, that the water wave function indeed exhibits equivalent lone pairs. The observed photoelectron spectrum is reconciled with this view, in terms of a relaxation of this structure upon the loss of an electron. Therefore, the lone-pair viewpoint is shown to be completely consistent with both the experimental results and the calculated wave function.
Methyl Substitution in Hydrocarbon Discharge Chemistry: Diagnosis by Laser Spectroscopy
Publisher: American Chemical Society (ACS)
Date: 08-2003
DOI: 10.1021/JP0349583
Sulfur terminated nanowires in the gas phase: laser spectroscopy and mass spectrometry
Publisher: Elsevier BV
Date: 04-2004
Quantum-Induced Symmetry-Breaking in the Deuterated Dihydroanthracenyl Radical
Publisher: American Chemical Society (ACS)
Date: 15-05-2019
DOI: 10.26434/CHEMRXIV.8123648
Abstract: The hydrogen-atom adduct with anthracene, 9-dihydroanthracenyl radical (C sub /sub H sub /sub ), and its deuterated analogue, have been identified by laser spectroscopy coupled to time-of-flight mass spectrometry, supported by time-dependent density functional theory calculations. The electronic spectrum of 9-dihydroanthracenyl radical exhibits an origin band at 19115 cm sup -1 /sup and its ionization energy was determined to be 6.346(1) eV. The spectra reveal a low-frequency vibrational progression corresponding to a mode described by a butterfly-inversion. In the deuterated analogue, a zero-point-energy imbalance along this coordinate is found to lead to a doubling of the observed spectral lines in the progression. This is attributed to quantum-induced symmetry breaking as previously observed in isotopologues of CH sub /sub sup + /sup .
Optimization of energy transfer in a polymer composite with perylene chromophores
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8TC02457J
Abstract: Luminescent solar concentrators based on molecular dyes are a promising approach to light collection.
Towards bulk behaviour of long hydrogenated carbon chains?
Publisher: Royal Society of Chemistry (RSC)
Date: 2003
DOI: 10.1039/B309100G
Ionization energies of three resonance-stabilized radicals: Cyclohexadienyl (dn , n = 0, 1, 6, 7), 1-phenylpropargyl, and methylcyclohexadienyl
Publisher: American Chemical Society (ACS)
Date: 22-10-2014
DOI: 10.1021/JP508985S
Abstract: The ionization energies for three resonance-stabilized radicals are determined: cyclohexadienyl, 1-phenylpropargyl, and methylcyclohexadienyl. The recommended ionization energies are, respectively, 6.820(1), 6.585(1), and 7.232(1) eV. That of cyclohexadienyl is found to be just 0.02 eV above a high level ab initio calculation [Bargholz, A. Oswald, R. Botschwina, P. J. Chem. Phys. 2013, 138, 014307], and that of 1-phenylpropargyl is found within the stated error of a recent experimental determination [Holzmeier, F. Lang, M. Hemberger, P. Fischer, I. ChemPhysChem 2014, DOI: 10.1002/cphc.201402446]. The ionization energy of the methylcyclohexadienyl radical is consistent with the ortho isomer. Ionization energies of a range of isotopologues of cyclohexadienyl radical are given, along with their D1 ← D0 origin band positions, which indicate a blue shift of 18 cm(-1) per deuterium atom substituted. The ionization energy of cyclohexadienyl, along with the calculated bond dissociation energy of Bargholz et al., affords a new estimate of the 0 K proton affinity of benzene: 739.7 ± 2.0 kJ/mol. The ionization energies are discussed in terms of the interplay between radical and cation stabilization energies.
Ultrafast Electron and Phonon Response of Oriented and Diameter-Controlled Germanium Nanowire Arrays
Publisher: American Chemical Society (ACS)
Date: 19-05-2014
DOI: 10.1021/NL500953P
Abstract: Carrier and phonon dynamics in dense arrays of aligned, single-crystal Ge nanowires (NWs) of controlled diameter are investigated by ultrafast optical pump-probe measurements, effective medium calculations, and elasticity analysis. Both a pronounced induced absorption and the litude and spectral range of Fabry-Perot oscillations observed in the probe signal are predicted for the NW array/air metamaterial by effective medium calculations. Detected temporal oscillations of reflectivity are consistent with excitation of radial breathing mode acoustic phonons by the intense pump pulse.
A molecular approach to the intermediate band solar cell: The symmetric case
Publisher: AIP Publishing
Date: 11-08-2008
DOI: 10.1063/1.2970157
Abstract: Molecular materials may overcome some of the difficulties for making an intermediate band solar cell by storing energy in long-lived triplet states. Both the problems of fast nonradiative interband relaxation and selective photon absorption can be solved by this approach. A practical implementation of the molecular intermediate band solar cell is considered with a symmetric band alignment, resting on a proven triplet-triplet annihilation process. The limiting power conversion efficiency for this system exceeds that of a single bandgap device over a broad range, peaking at 40.6% for 1.9eV under 1 sun illumination.
A Marcus-Hush Perspective on Adiabatic Singlet Fission
Publisher: American Chemical Society (ACS)
Date: 25-04-2019
DOI: 10.26434/CHEMRXIV.8038892.V1
Abstract: Singlet fission is a process whereby a bichromophoric system crosses from an excitonically coupled singlet state to a singlet-coupled triplet pair state. If the electronic structure is described locally, then the process may be described by a formal exchange of electrons. As such, it lends itself to a treatment rooted in the Marcus-Hush description of electron transfer. Here we use ab initio and density functional electronic structure theories to reveal a Marcus-Hush perspective on singlet fission and propose experiments to probe singlet fission in the spirit of photo-induced electron transfer.
The Optical Spectroscopy of Extraterrestrial Molecules
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/CH04269
Abstract: The ongoing quest to identify molecules in the interstellar medium by their electronic spectra in the visible region is reviewed. Identification of molecular absorption is described in the context of the elucidation of the carriers of the unidentified Diffuse Interstellar Bands, and molecular emission is discussed with reference to the unidentified Red Rectangle bands. The experimental techniques employed in undertaking studies on the optical spectroscopy of extraterrestrial molecules are described and critiqued in the context of their application.
Higher vibrational levels of the D 1
Publisher:
Elsevier BV
Date:
02-2018
Publisher: Elsevier BV
Date: 02-2018
The ionization energy of C2
Publisher: AIP Publishing
Date: 11-04-2016
DOI: 10.1063/1.4944932
Abstract: Resonant two-photon threshold ionization spectroscopy is employed to determine the ionization energy of C2 to 5 meV precision, about two orders of magnitude more precise than the previously accepted value. Through exploration of the ionization threshold after pumping the 0–3 band of the newly discovered 43Πg←a3Πu band system of C2, the ionization energy of the lowest rovibronic level of the a3Πu state was determined to be 11.791(5) eV. Accounting for spin-orbit and rotational effects, we calculate that the ionization energy of the forbidden origin of the a3Πu state is 11.790(5) eV, in excellent agreement with quantum thermochemical calculations which give 11.788(10) eV. The experimentally derived ionization energy of X1Σg+ state C2 is 11.866(5) eV.
Electronic spectrum of 9-methylanthracenium radical cation
Publisher: AIP Publishing
Date: 18-04-2016
DOI: 10.1063/1.4945109
Abstract: The predissociation spectrum of the cold, argon-tagged, 9-methylanthracenium radical cation is reported from 8000 cm−1 to 44 500 cm−1. The reported spectrum contains bands corresponding to at least eight electronic transitions ranging from the near infrared to the ultraviolet. These electronic transitions are assigned through comparison with ab initio energies and intensities. The infrared D1←D0 transitions exhibit significant vibronic activity, which is assigned through comparison with TD-B3LYP excited state frequencies and intensities, as well as modelled vibronic interactions. Dissociation of 9-methylanthracenium is also observed at high visible-photon energies, resulting in the loss of either CH2 or CH3. The relevance of these spectra, and the spectra of other polycyclic aromatic hydrocarbon radical cations, to the largely unassigned diffuse interstellar bands, is discussed.
On the efficiency limit of triplet-triplet annihilation for photochemical upconversion
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B913243K
Abstract: Photochemical upconversion is performed, whereby emitter triplet states are produced through triplet energy transfer from sensitizer molecules excited with low energy photons. The triplet emitter molecules undergo triplet-triplet annihilation to yield excited singlet states which emit upconverted fluorescence. Experiments comparing the 560 nm prompt fluorescence when rubrene emitter molecules are excited directly, using 525 nm laser pulses, to the delayed, upconverted fluorescence when the porphyrin sensitizer molecules are excited with 670 nm laser pulses reveal annihilation efficiencies to produce excited singlet emitters in excess of 20%. Conservative measurements reveal a 25% annihilation efficiency, while a direct comparison between the prompt and delayed fluorescence yield suggests a value as high as 33%. Due to fluorescence quenching, the photon upconversion efficiencies are lower, at 16%.
Harnessing Sunlight via Molecular Photon Upconversion
Publisher: American Chemical Society (ACS)
Date: 06-07-2021
Astronomical Molecular Spectroscopy
Publisher: Wiley
Date: 11-10-2010
Quantifying the Relaxation Dynamics of Higher Electronic Excited States in Perylene
Publisher: American Chemical Society (ACS)
Date: 31-08-2023
The Electronic Structure of Water: Pulling Rabbit-Ears out of a Wave Function
Publisher: American Chemical Society (ACS)
Date: 10-07-2019
DOI: 10.26434/CHEMRXIV.8847947.V1
Abstract: The electronic structure of water is typically thought of exhibiting lone-pairs of electrons, described by some as "rabbit-ears'". This is not the universal view, and does not mesh with an interpretation based on the one-electron wavefunctions which emerge from molecular orbital theory. Here we show, by analysing the antisymmetrized wavefunction (Slater determinant) rather than the Hartree product, that the water wavefunction indeed exhibits equivalent lone pairs. The observed photoelectron spectrum is reconciled with this view in terms of a relaxation of this structure upon the loss of an electron. It is therefore shown that the lone-pair viewpoint is completely consistent with both the experimental results and the calculated wavefunction.
Simulations of Luminescent Solar Concentrator Bifacial Photovoltaic Mosaic Devices Containing Four Different Organic Luminophores
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2022
Electronic Wavefunction Tiles
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CH19517
Abstract: We review the pre-quantum theories of electronic structure of Lewis and Langmuir, and how this relates to the post-quantum double-quartet theory of Linnett. Linnett’s ideas are put on a firm theoretical footing through the emergence of the wavefunction tile: The 3N-dimensional repeating structure of the N-electron wavefunction. Wavefunction tiles calculated by the dynamic Voronoi Metropolis s ling method are reviewed, and new results are presented for bent bonds of cyclopropane, and electron correlation in Be-O-Be.
Molecular Polarization Switching for Improved Light Coupling in Luminescent Solar Concentrators
Publisher: American Chemical Society (ACS)
Date: 13-08-2013
DOI: 10.1021/JZ4013905
An agnostic approach
Publisher: Springer Science and Business Media LLC
Date: 12-2013
The Hitchhiker’s Guide to the Wave Function
Publisher: American Chemical Society (ACS)
Date: 31-01-2022
Abstract: The electronic wave function of molecules is 3
Dye-sensitized solar cell with integrated triplet-triplet annihilation upconversion system
Publisher: American Chemical Society (ACS)
Date: 11-06-2013
DOI: 10.1021/JZ401050U
Abstract: Photon upconversion (UC) by triplet-triplet annihilation (TTA-UC) is employed in order to enhance the response of solar cells to sub-bandgap light. Here, we present the first report of an integrated photovoltaic device, combining a dye-sensitized solar cell (DSC) and TTA-UC system. The integrated device displays enhanced current under sub-bandgap illumination, resulting in a figure of merit (FoM) under low concentration (3 suns), which is competitive with the best values recorded to date for nonintegrated systems. Thus, we demonstrate both the compatibility of DSC and TTA-UC and a viable method for device integration.
Characterization of the Ã(1A″) state of HCF by laser induced fluorescence spectroscopy
Publisher: AIP Publishing
Date: 15-06-1999
DOI: 10.1063/1.479068
Abstract: An extensive experimental exploration of the Ã(1A″)←X̃(1A′) transition of supersonically cooled fluoromethylene has been performed using laser induced fluorescence spectroscopy. Several new bending vibrational bands are reported, which provide the harmonic frequency and anharmonicity constant for this vibration and lead to an estimate of the height of the barrier to linearity as 6400±500 cm−1. Assignment of the vibrational hot-band structure leads to the first measurement of the à state CF stretching frequency as ν3′=1260 cm−1 and tentatively the CH stretching frequency as ν1′=2852 cm−1. The A′ rotational constant increases strongly with increasing quanta of bending vibration, which indicates that the molecular structure is becoming more linear. Consideration of only the average bond angle, calculated from ab initio data for this state, is insufficient to account for the change in A′. The coupling of a-axis rotation with bending vibration must be included. A number of other dynamical effects were observed in the spectra, including lifetime shortening and disappearance of rotational transitions with K′⩾1. These were explained in terms of the Renner–Teller interaction between the X̃ and à states.
Electronic photodissociation spectra of the Arn–C4H2+ (n=1–4) weakly bound cationic complexes
Publisher: Elsevier BV
Date: 11-2003
Optical detection of C9H3, C11H3, and C13H3 from a hydrocarbon discharge source
Publisher: Elsevier BV
Date: 08-2003
An All-Photonic Molecular Amplifier and Binary Flip-flop
Publisher: American Chemical Society (ACS)
Date: 25-11-2020
DOI: 10.26434/CHEMRXIV.13277855
Abstract: A chemical system is proposed that is capable of lifying small optical inputs into large changes in internal composition, based on a feedback interaction between switchable fluorescence and visible-light photoswitching. This system would demonstrate bifurcating reaction kinetics under irradiation and reach one of two stable photostationary states depending on the initial composition of the system. This behavior would allow the system to act as a chemical realization of the flip-flop circuit, the fundamental element in sequential logic and binary memory storage. We use detailed numerical modeling to demonstrate the feasibility of the proposed behavior based on known molecular phenomena, and comment on some of the conditions required to realize this system.
Gas phase spectra of all-benzenoid polycyclic aromatic hydrocarbons: Triphenylene
Publisher: AIP Publishing
Date: 22-02-2007
DOI: 10.1063/1.2484344
Abstract: The jet-cooled laser-induced fluorescence and dispersed fluorescence spectra of the S1(A1′)←S0(A1′) transition of triphenylene are reported. The spectra exhibit false origins of e′ symmetry which are modeled by performing calculations of Herzberg-Teller coupling using time-dependent density functional theory. It is found that this level of theory reproduces the main features of the observed spectra. The oscillator strength of the strongest band is calculated to be f=7×10−4. From a combination of theory and the observed upper state lifetime of 41ns, an estimate of the fluorescence yield is made of ΦF=0.084, in agreement with previous studies in the condensed phase.
Atmospheric oxidation intermediates: Laser spectroscopy of resonance-stabilized radicals from p-cymene
Publisher: Elsevier BV
Date: 2015
Femtosecond fluorescence depletion spectroscopy of NO2 multiphoton dissociation dynamics
Publisher: AIP Publishing
Date: 22-10-1999
DOI: 10.1063/1.480046
Abstract: Two-color femtosecond pump–probe spectroscopy has been applied to the multiphoton dissociation of NO2 with a time resolution of ⩽350 fs. At laser intensities in the range ≃3×1012–2×1013 W cm−2 and a wavelength of 400 nm, NO2 absorbs three photons before dissociation. Nascent NO A 2Σ+ product in its n′=0 and 1 vibrational levels is probed by single-photon fluorescence depletion at 800 nm. Analyses of the ultrafast transient behavior at different intensities leads to an estimate of ⩽600 fs for formation of NO A 2Σ+ n′=0 and 1.
A Marcus-Hush perspective on adiabatic singlet fission
Publisher: AIP Publishing
Date: 02-08-2019
DOI: 10.1063/1.5108669
Abstract: Singlet fission is a process whereby a bichromophoric system crosses from an excitonically coupled singlet state to a singlet-coupled triplet pair state. If the electronic structure is described locally, then the process may be described by a formal exchange of electrons. As such, it lends itself to a treatment rooted in the Marcus-Hush description of electron transfer. Here, we use ab initio and density functional electronic structure theories to reveal a Marcus-Hush perspective on singlet fission and propose experiments to probe singlet fission in the spirit of photo-induced electron transfer.
Optimizing the Efficiency of Solar Photon Upconversion
Publisher: American Chemical Society (ACS)
Date: 11-05-2017
Molecular approaches to third generation photovoltaics: Photochemical up-conversion
Publisher: SPIE
Date: 19-08-2010
DOI: 10.1117/12.862739
Ultrafast Carrier Dynamics of a Photo-Excited Germanium Nanowire–Air Metamaterial
Publisher: American Chemical Society (ACS)
Date: 21-07-2015
Rotationally-resolved excitation spectrum of the jet-cooled cyclohexadienyl radical
Publisher: Elsevier BV
Date: 11-2007
Photochemical upconversion enhanced solar cells: Effect of a back reflector
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/CH12117
Abstract: Photochemical upconversion is applied to a hydrogenated amorphous silicon solar cell in the presence of a back-scattering layer. A custom-synthesized porphyrin was utilized as the sensitizer species, with rubrene as the emitter. Under a bias of 24 suns, a peak external quantum efficiency (EQE) enhancement of ~2 % was observed at a wavelength of 720 nm. Without the scattering layer, the EQE enhancement was half this value, indicating that the effect of the back-scatterer is to double the efficacy of the upconverting device. The results represent an upconversion figure of merit of 3.5 × 10–4 mA cm–2 sun–2, which is the highest reported to date.
All-optical augmentation of solar cells using a combination of up- and downconversion
Publisher: SPIE-Intl Soc Optical Eng
Date: 28-03-2018
TIPS-anthracene: a singlet fission or triplet fusion material?
Publisher: SPIE-Intl Soc Optical Eng
Date: 30-03-2018
Triple-Resonance Spectroscopy Reveals the Excitation Spectrum of Very Cold, Isomer-Specific Protonated Naphthalene
Publisher: American Chemical Society (ACS)
Date: 21-10-2013
DOI: 10.1021/JZ401986T
PAH growth in flames and space: Formation of phenalenyl radical
Publisher: American Chemical Society (ACS)
Date: 03-09-2021
DOI: 10.26434/CHEMRXIV-2021-P9XR8
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are intermediates in the formation of soot particles and interstellar grains. However, their formation mechanisms in combustion and interstellar environments are not fully understood. The production of tricyclic PAHs and, in particular, the conversion of a PAH containing a five-membered ring to one with a six-membered ring is of interest to explain PAH abundances in combustion processes. In the present work, resonant ionization mass spectrometry in conjunction with isotopic labelling is used to investigate the formation of the phenalenyl radical from acenaphthylene and methane in an electrical discharge. We show that in this environment, the CH cycloaddition mechanism converts a five-membered ring to a six-membered ring. This mechanism can occur in tandem with other PAH formation mechanisms such as hydrogen abstraction/ acetylene addition (HACA) to produce larger PAHs in flames and the interstellar medium.
Open questions on carbon-based molecules in space
Publisher: Springer Science and Business Media LLC
Date: 10-08-2022
Photochemical upconversion of light for renewable energy and more
Publisher: SPIE
Date: 04-09-2015
DOI: 10.1117/12.2195424
Highly efficient photochemical upconversion in a quasi-solid organogel
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4TC02584A
Abstract: Photochemical upconversion in a quasi-solid gel proceeds with an identical efficiency to an otherwise identical liquid composition.
Intense-field modulation of NO2 multiphoton dissociation dynamics
Publisher: AIP Publishing
Date: 18-08-2004
DOI: 10.1063/1.1775768
Abstract: We report on the dynamics of multiphoton excitation and dissociation of NO2 at wavelengths between 395 and 420 nm and intensities between 4 and 10 TW cm−2. The breakup of the molecule is monitored by NO A 2Σ+n′=1,0→X 2Πrn″=0 fluorescence as a function of time delay between the driving field and a probe field which depletes the emission. It is found that generation of n′=0 and 1 NO A 2Σ+ results in different fluorescence modulation patterns due to the intense probe field. The dissociation dynamics are interpreted in terms of nuclear motions over light-induced potentials formed by coupling of NO2 valence and Rydberg states to the applied field. Based on this model, it is argued that the time and intensity dependences of A 2Σ+n′=0→X 2Πrn″=0 fluorescence are consistent with delayed generation of NO A 2Σ+n′=0 via a light-induced bond-hardening brought about by the transient coupling of the dressed à 2B2 and Rydberg 3sσ Σg+2 states of the parent molecule. The increasingly prompt decay of A 2Σ+n′=1→X 2Πrn″=0 fluorescence with increasing intensity, on the other hand, is consistent with a direct surface crossing between the X̃ 2A1 and 3sσ Σg+2 dressed states to generate vibrationally excited products.
Publisher’s Note: “Laser-induced fluorescence and dispersed fluorescence spectroscopy of jet-cooled 1-phenylpropargyl radical” [J. Chem. Phys. 130, 144313 (2009)]
Publisher: AIP Publishing
Date: 10-07-2009
DOI: 10.1063/1.3171934
The Spectroscopy of C2: A Cosmic Beacon
Publisher: American Chemical Society (ACS)
Date: 13-01-2021
Hydrogen-adduction to open-shell graphene fragments: spectroscopy, thermochemistry and astrochemistry
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6SC03787A
Abstract: H-Adducted graphene fragments are interrogated with lasers, revealing excited state bond dissociation energies and ionization energies.
A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A
Publisher: American Astronomical Society
Date: 12-2022
Abstract: We characterize massive stars ( M 8 M ⊙ ) in the nearby ( D ∼ 0.8 Mpc) extremely metal-poor ( Z ∼ 5% Z ⊙ ) galaxy Leo A using Hubble Space Telescope ultraviolet (UV), optical, and near-infrared (NIR) imaging along with Keck/Low-Resolution Imaging Spectrograph and MMT/Binospec optical spectroscopy for 18 main-sequence OB stars. We find that: (a) 12 of our 18 stars show emission lines, despite not being associated with an H ii region, suggestive of stellar activity (e.g., mass loss, accretion, binary star interaction), which is consistent with previous predictions of enhanced activity at low metallicity (b) six are Be stars, which are the first to be spectroscopically studied at such low metallicity—these Be stars have unusual panchromatic SEDs (c) for stars well fit by the TLUSTY nonlocal thermodynamic equilibrium models, the photometric and spectroscopic values of log ( T eff ) and log ( g ) agree to within ∼0.01 dex and ∼0.18 dex, respectively, indicating that near-UV/optical/NIR imaging can be used to reliably characterize massive ( M ∼ 8–30 M ⊙ ) main-sequence star properties relative to optical spectroscopy (d) the properties of the most-massive stars in H II regions are consistent with constraints from previous nebular emission line studies and (e) 13 stars with M 8 M ⊙ are pc from a known star cluster or H II region. Our s le comprises ∼50% of all known massive stars at Z ≲ 10% Z ⊙ with derived stellar parameters, high-quality optical spectra, and panchromatic photometry.
Gas-phase spectroscopy of the 2 Σ3−−X̃ Σ3− electronic transition of CCS
Publisher: AIP Publishing
Date: 06-01-2009
DOI: 10.1063/1.3042269
Abstract: Gas-phase laser excitation spectra of the jet-cooled CCS radical were observed for the 2 Σ3−−X̃ Σ3− electronic transition in a discharge of a gas mixture containing acetylene and H2S in Ar. The observed excitation spectra show complicated rotational structures, consisting of a much larger number of rotational lines than those expected for this size of linear molecule. The excited vibronic levels emit fluorescence, the lifetime of which is much longer than that estimated theoretically, indicating that the upper levels are strongly mixed with many “dark” background levels. Dispersed fluorescence spectra from single vibrational levels of the 2 Σ3− state show long progressions of the C–S stretching mode, enabling observations of many vibrational levels in the ground electronic state.
Charge Transfer-Mediated Multi-exciton Mechanisms in Weakly Coupled Perylene Dimers
Publisher: American Chemical Society (ACS)
Date: 21-08-2023
Consensus statement: Standardized reporting of power-producing luminescent solar concentrator performance
Publisher: Elsevier BV
Date: 2022
Singlet fission photovoltaics: Progress and promising pathways
Publisher: AIP Publishing
Date: 11-05-2022
DOI: 10.1063/5.0080250
Abstract: Singlet fission is a form of multiple exciton generation, which occurs in organic chromophores when a high-energy singlet exciton separates into two lower energy triplet excitons, each with approximately half the singlet energy. Since this process is spin-allowed, it can proceed on an ultrafast timescale of less than several picoseconds, outcompeting most other loss mechanisms and reaching quantitative yields approaching 200%. Due to this high quantum efficiency, the singlet fission process shows promise as a means of reducing thermalization losses in photovoltaic cells. This would potentially allow for efficiency improvements beyond the thermodynamic limit in a single junction cell. Efforts to incorporate this process into solar photovoltaic cells have spanned a wide range of device structures over the past decade. In this review, we compare and categorize these attempts in order to assess the state of the field and identify the most promising avenues of future research and development.
Gas phase electronic spectra of the linear carbon chains HC2n+1H (n=3–6,9)
Publisher: AIP Publishing
Date: 26-06-2003
DOI: 10.1063/1.1578476
Abstract: The B 3Σu−←X 3Σg− transitions of HC13H and HC19H have been measured in the gas phase, exhibiting broad, Lorentzian shaped bands. More extensive A 3Σu−←X 3Σg− spectra have been observed for HC2n+1H (n=3–6) than before with many new vibronic bands identified. The spectra were obtained by means of a mass selective resonant two-color two-photon ionization technique coupled to a supersonic plasma source. The electronic structures of this series of molecules (n=2–9) in both the ground and excited states have been investigated using DFT, MP2, and state-averaged CASSCF theories. The three lowest dipole allowed electronic transition systems are A 3Σu−←X 3Σg−, B 3Σu−←X 3Σg−, and C 3Πu←X 3Σg−, located, for the smaller members of the series, in the visible, UV and VUV range, respectively. The A 3Σu−←X 3Σg− system is found to be of medium intensity and the B 3Σu−←X 3Σg− transition is predicted to be very strong. This is a result of configuration mixing in the excited states. The oscillator strength of the lowest energy transition is not strongly dependent on the length of the chain, but that of the B 3Σu−←X 3Σg− system increases monotonically with size. The C 3Πu state is Rydberg in character. The astrophysical implications are considered and an upper limit of the column densities of these carbon chains in diffuse clouds has been estimated as 1013 cm−2, based on calculated oscillator strengths.
Improving the light-harvesting of second generation solar cells with photochemical upconversion
Publisher: SPIE
Date: 27-09-2012
DOI: 10.1117/12.945217
An intermediate band dye-sensitised solar cell using triplet–triplet annihilation
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5CP04825G
Abstract: A new mechanism of charge photogeneration is demonstrated for the first time, based on organic molecular structures.
Morphological Evolution and Singlet Fission in Aqueous Suspensions of TIPS-Pentacene Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 29-12-2016
Competing Energy Transfer Pathways in a Five-Chromophore Perylene Array
Publisher: American Chemical Society (ACS)
Date: 24-02-2018
Towards an aligned luminophore solar concentrator
Publisher: Optica Publishing Group
Date: 26-05-2010
DOI: 10.1364/OE.18.00A161
Photochemical upconversion: present status and prospects for its application to solar energy conversion
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4EE02481H
Abstract: We review the application of sensitized triplet–triplet annihilation upconversion to broaden the harvested spectrum of solar energy conversion devices.
An All-Photonic Molecular Amplifier and Binary Flip-flop
Publisher: American Chemical Society (ACS)
Date: 25-01-2021
Quantum chemical studies of the potential energy surfaces and vibrational frequencies of the??(1A?),�(3A?), and�(1A?) states of CHCl and CFCl
Publisher: Wiley
Date: 2000
DOI: 10.1002/(SICI)1097-461X(2000)76:3<297::AID-QUA1>3.0.CO;2-V
Electronic Transitions of Molecules: Vibrating Lewis Structures
Publisher: American Chemical Society (ACS)
Date: 21-03-2019
DOI: 10.26434/CHEMRXIV.7871921
Abstract: In this work we demonstrate a simple and intuitive description of electronic resonances in terms of localized electron vibrations. By partitioning the 3N-dimensional space of a many-electron wavefunction into hyper-regions related by permutation symmetry, chemical structures naturally result which correspond closely to Lewis structures, with identifiable single and double bonds, and lone pairs. Here we demonstrate how this picture of electronic structure develops upon the admixture of electronic wavefunctions, in the spirit of coherent electronic transitions. We show that pi-pi* transitions correspond to double-bonding electrons oscillating along the bond axis, and n-pi* transitions reveal lone-pairs vibrating out of plane. In butadiene and hexatriene, the double-bond oscillations combine with in- and out-of-phase combinations, revealing the correspondence between electronic transitions, molecular normal mode vibrations, and molecular plasmonics. This analysis allows electronic excitations to be described by building upon ground state electronic structures, without the need for molecular orbitals.
Velocity map imaging spectroscopy of C2H− and C2D−: A benchmark study of vibronic coupling interactions
Publisher: AIP Publishing
Date: 28-07-2022
DOI: 10.1063/5.0100297
Abstract: High-resolution velocity-map imaged photoelectron spectra of the ethynyl anions C2H− and C2D− are measured at photon wavelengths between 355 and 266 nm to investigate the complex interactions between the closely lying X̃2Σ+ and Ã2Π electronic states. An indicative kinetic energy resolution of 0.4%, together with the full angular dependence of the fast electrons, provides a detailed description of the vibronically coupled structure. It is demonstrated that a modest quadratic vibronic coupling model, parameterized by the quasidiabatic ansatz, is sufficient to accurately recreate all the observed vibronic interactions. Simulated spectra are shown to be in excellent agreement with the experimental data, verifying the proposed model and providing a framework that may be used to accurately simulate spectra of larger C2nH monohydride carbon chains. New spectral assignments are supported by experimental electron anisotropy measurements and Dyson orbital calculations.
Photochemical Upconversion Theory: Importance of Triplet Energy Levels and Triplet Quenching
Publisher: American Physical Society (APS)
Date: 13-08-2019
Visible Photodissociation Spectra of the 1- and 2-Methylnaphthalene Cations: Laser Spectroscopy and Theoretical Simulations
Publisher: American Chemical Society (ACS)
Date: 31-10-2013
DOI: 10.1021/JP407627X
Abstract: The electronic absorption spectra of the two methyl derivatives of the naphthalene cation were measured using an argon tagging technique. In both cases, a band system was observed in the visible range and assigned to the D2 ← D0 electronic transition. The 1-methylnaphthalene(+) absorption bands revealed a red shift of 808 cm(-1), relative to those of the naphthalene cation (14,906 cm(-1)), whereas for 2-methylnaphthalene(+) a blue shift of 226 cm(-1) appeared. A short vibrational progression, similar to the naphthalene cation, was also observed for both isomers and found to involve similar aromatic ring skeleton vibrations. Moreover, insights into the internal rotation motion of the methyl group were inferred, although the spectral resolution was not sufficient to fully resolve the substructure. These measurements were supported by detailed quantum chemical calculations. They allowed exploration of the potential energy curves along this internal coordinate, along with a complete simulation of the harmonic Franck-Condon factors using the cumulant Gaussian fluctuations formalism extended to include the internal rotation.
New Laboratory Data on a Molecular Band at 4429 A
Publisher: American Astronomical Society
Date: 12-2004
DOI: 10.1086/424959
Entropically Driven Photochemical Upconversion
Publisher: American Chemical Society (ACS)
Date: 25-01-2011
DOI: 10.1021/JP108839G
Abstract: Conventional photochemical upconversion (UC) through homo-geneous triplet-triplet annihilation (TTA) is subject to several enthalpic losses that limit the UC margin. Here, we address one of these losses: the triplet energy transfer (TET) from the sensitizer to the emitter molecules. Usually, the triplet energy level of the emitter is set below that of the sensitizer. In our system, the triplet energy level of the emitter exceeds that of the sensitizer by ∼600 cm(-1). Choosing suitable concentrations for the sensitizer and emitter molecules, we can exploit entropy as a driving force for the migration of triplet excitation from the sensitizer to the emitter manifolds. Thereby we obtain a new record for the peak-to-peak TTA-UC energy margin of 0.94 eV. A modified Stern-Volmer analysis yields a TET rate constant of 2.0 × 10(7) M(-1) s(-1). Despite being relatively inefficient, the upconverted fluorescence is easily visible to the naked eye with irradiation intensities as low as 2 W cm(-2).
Oscillator strengths of the Mulliken, Swan, Ballik-Ramsay, Phillips, and dΠg3←cΣu+3 systems of C2 calculated by MRCI methods utilizing a biorthogonal transformation of CASSCF orbitals
Publisher: AIP Publishing
Date: 19-12-2007
DOI: 10.1063/1.2806988
Abstract: Ab initio oscillator strengths and lifetimes for the DΣu+1←XΣg+1 Mulliken system of C2 are reported. The calculations were carried out at the MRCI level of theory with Davidson’s correction using aug-cc-pV6Z basis sets and include core and core-valence correlation as well as relativistic corrections, computed with aug-cc-pCVQZ and cc-pVQZ bases, respectively. The MRCI calculations of transition moments utilize a biorthogonal transformation of the CASSCF orbitals. This approach was also employed to recompute the transition moments of the Swan, Ballik-Ramsay, Phillips, and dΠg3←cΣu+3 systems of C2, which were the subject of our previous study [D. L. Kokkin et al., J. Chem. Phys. 126, 084302 (2007)], resulting in an improved set of oscillator strengths for the latter systems as well. The oscillator strength of the Mulliken origin band, f00DA, was calculated to be 0.0535, in excellent agreement with the accepted astronomical value of 0.054.
Nanostructured upconverters for improved solar cell performance
Publisher: SPIE
Date: 25-09-2013
DOI: 10.1117/12.2026907
The Electronic Structure of Water: Pulling Rabbit-Ears out of a Wave Function
Publisher: American Chemical Society (ACS)
Date: 10-07-2019
DOI: 10.26434/CHEMRXIV.8847947
Abstract: The electronic structure of water is typically thought of exhibiting lone-pairs of electrons, described by some as "rabbit-ears'". This is not the universal view, and does not mesh with an interpretation based on the one-electron wavefunctions which emerge from molecular orbital theory. Here we show, by analysing the antisymmetrized wavefunction (Slater determinant) rather than the Hartree product, that the water wavefunction indeed exhibits equivalent lone pairs. The observed photoelectron spectrum is reconciled with this view in terms of a relaxation of this structure upon the loss of an electron. It is therefore shown that the lone-pair viewpoint is completely consistent with both the experimental results and the calculated wavefunction. br /
Observation of the predissociated, quasilinear B̃(A′1) state of CHF by optical-optical double resonance
Publisher: AIP Publishing
Date: 07-02-2007
DOI: 10.1063/1.2515273
Abstract: We report the first observation of the predissociative B̃ state of a halocarbene molecule. Rovibronic energy levels were measured in the B̃(A′1) state of CHF by fluorescence dip detected optical-optical double resonance spectroscopy via the à state. The origin was found to lie 30817.4cm−1 above the zero point level of the X̃ state. Rotational transitions within six purely bending states, and states involving one or two quanta of CF-stretch were observed, including the vibrational angular momentum components. Interpretation of the spectrum, with support of ab initio calculations, shows that CHF is quasilinear in the B̃ state with a small (−200cm−1) barrier to linearity which lies below the zero-point level. The rotational constant, B=1.04 to 1.09cm−1, depending on vibrational state, again in good agreement with theory. All observed B̃ state levels were predissociative, as evidenced by Lorentzian line broadening. Linewidths varied with initial state from 0.7–10.8cm−1, corresponding to excited state lifetimes of 0.5–8ps.
Current assessment of the Red Rectangle band problem
Publisher: Springer Science and Business Media LLC
Date: 11-09-2009
Comment on “Tremendously enhanced photocurrent enabled by triplet–triplet annihilation up-conversion for high-performance perovskite solar cells” by W. Sheng, J. Yang, X. Li, G. Liu, Z. Lin, J. Long,
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1EE01446C
Abstract: We discuss why in the device structure presented Sheng et al. upconversion inherently cannot be the underlying cause of the observed effects.
An experimental and theoretical study on vibrational structure in the B̃–X̃ transition of CH2CHS
Publisher: AIP Publishing
Date: 14-09-2009
DOI: 10.1063/1.3224146
Abstract: An electronic excitation spectrum of the B̃–X̃ transition of the CH2CHS (vinylthio, thiovinoxy) radical was observed in the range of 21 800–23 400 cm−1 by fluorescence depletion spectroscopy. Vibrational assignments for the depletion spectrum were made with the help of a theoretical excitation spectrum computed from results of ab initio calculations. The previously observed emission spectrum [M. Nakajima et al., J. Chem. Phys. 126, 044307 (2007)] was also reassigned based on the present theoretical study. Rotational band contours observed in the depletion spectrum show a large variation due to a vibrational-level dependence of the excited state lifetime. However, no obvious vibrational mode dependence of the lifetime was observed.
Observation of the dΠg3←cΣu+3 band system of C2
Publisher: AIP Publishing
Date: 18-12-2006
DOI: 10.1063/1.2408412
Abstract: A new band system of C2, dΠg3←cΣu+3 is observed by laser induced fluorescence spectroscopy, constituting the first direct detection of the cΣu+3 state of C2. Observations were made by laser excitation of cΣu+3(v″=0) C2, produced in an acetylene discharge, to the dΠg3(v′=3) level, followed by detection of Swan band fluorescence. Rotational analysis of this band yielded rotational constants for the cΣu+3(v″=0) state: B0=1.9218(2)cm−1, λ0=−0.335(4)cm−1 and γ0=0.011(2)cm−1. The vibrational band origin was determined to be ν3−0=15861.28cm−1.
The C−H Stretch Intensities of Polycyclic Aromatic Hydrocarbon Cations. Origins and Astrophysical Implications
Publisher: American Chemical Society (ACS)
Date: 25-03-2009
DOI: 10.1021/JP900931E
Abstract: Infrared vibrational transition intensities of polycyclic aromatic hydrocarbons are known to depend strongly on the charge state. The detailed understanding of this effect for the C-H stretching modes has been approached by applying the quantum theory of atoms in molecules. Several benchmark calculations were undertaken in order to disentangle charge and size effects, from benzene (C(6)H(6)) up to the ovalene (C(32)H(14)) molecule. Upon decomposition of the dipole moment derivative along a C-H stretch into charge, charge flux, and dipole flux terms, it is found that it is the competition between the sum of the first two terms and the latter which drives the intensity, due to their opposing signs. Additionally, while the dipole flux term changes very little with size and charge, the other terms are strongly sensitive to these. This effect leads to a very weak C-H stretch intensity for cation sizes close to pyrene (C(16)H(10)) and comparable intensities between neutral and cations for the much larger ones. The astrophysical implications are discussed.
Effect of gold nanoparticle shapes for phototherapy and drug delivery
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6PY00465B
Abstract: In this study, we compared three different hybrid gold nanoparticle shapes (spherical, rod and star) for photothermal therapy and the delivery of doxorubicin.
Experimental and theoretical investigation of the dispersed fluorescence spectroscopy of HC4S
Publisher: AIP Publishing
Date: 18-05-2006
DOI: 10.1063/1.2196886
Abstract: A high-resolution single vibronic level emission study from the ÃΠ3∕22 state of the HC4S radical is reported. Ground state density functional theory frequencies have been used to assign ground state vibronic levels involving three stretching modes ν2, ν3, and ν5 in the region of 0–3250cm−1, while the frequency of ν4 remains speculative. Tentative assignments are given for the complicated structures arising from Renner-Teller and spin-orbit interactions within the bending energy levels. From analysis of the dispersed emission spectra, Fermi resonances involving pairs of bands have been identified in the ÃΠ3∕22←X̃Π3∕22 laser induced fluorescence spectrum.
Challenges, progress and prospects in solid state triplet fusion upconversion
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1TC05659J
Abstract: Photon upconversion (UC) stands for the conversion of low to high energy photons, a promising approach to improve solar cells. While high efficiencies can be obtained in liquid UC, will a solid UC device be able to reach such levels?
Multihydroxy‐Anthraquinone Derivatives as Free Radical and Cationic Photoinitiators of Various Photopolymerizations under Green LED
Publisher: Wiley
Date: 20-04-2018
Abstract: Multihydroxy-anthraquinone derivatives [i.e., 1,2,4-trihydroxyanthraquinone (124-THAQ), 1,2,7-trihydroxyanthraquinone (127-THAQ), and 1,2,5,8-tetrahydroxyanthraquinone (1258-THAQ)] can interact with various additives [e.g., iodonium salt, tertiary amine, N-vinylcarbazole, and 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine] under household green LED irradiation to generate active species (cations and radicals). The relevant photochemical mechanism is investigated using quantum chemistry, fluorescence, cyclic voltammetry, laser flash photolysis, steady state photolysis, and electron spin resonance spin-trapping techniques. Furthermore, the multihydroxy-anthraquinone derivative-based photoinitiating systems are capable of initiating cationic photopolymerization of epoxides or inyl ethers under green LED, and the relevant photoinitiation ability is consistent with the photochemical reactivity (i.e., 124-THAQ-based photoinitiating system exhibits highest reactivity and photoinitiation ability). More interestingly, multihydroxy-anthraquinone derivative-based photoinitiating systems can initiate free radical crosslinking or controlled (i.e., reversible addition-fragmentation chain transfer) photopolymerization of methacrylates under green LED. It reveals that multihydroxy-anthraquinone derivatives can be used as versatile photoinitiators for various types of photopolymerization reactions.
Special section guest editorial: Spectral management for renewable energy conversion
Publisher: SPIE-Intl Soc Optical Eng
Date: 15-06-2018
Intramolecular hole-transfer in protonated anthracene
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP02922K
Abstract: Triple-resonance dissociation spectra of protonated and deuteronated anthracene reveal signatures of an intramolecular charge-transfer event that occurs on the excited state surface.
Laser-induced fluorescence and dispersed fluorescence spectroscopy of jet-cooled 1-phenylpropargyl radical
Publisher: AIP Publishing
Date: 13-04-2009
DOI: 10.1063/1.3110682
Abstract: The D1(A2″)−D0(A2″) electronic transition of the resonance-stabilized 1-phenylpropargyl radicalooled discharge of 3-phenyl-1-propyne, has been investigated in detail by laser-induced fluorescence excitation and dispersed single vibronic level fluorescence (SVLF) spectroscopy. The transition is dominated by the origin band at 21 007 cm−1, with weaker Franck–Condon activity observed in a′ fundamentals and even overtones and combinations of a″ symmetry. Ab initio and density functional theory calculations of the D0 and D1 geometries and frequencies were performed to support and guide the experimental assignments throughout. Analysis of SVLF spectra from 16 D1 vibronic levels has led to the assignment of 15 fundamental frequencies in the excited state and 19 fundamental frequencies in the ground state assignments for many more normal modes not probed directly by fluorescence spectroscopy are also suggested. Duschinsky mixing, in which the excited state normal modes are rotated with respect to the ground state modes, is prevalent throughout, in vibrations of both a′ and a″ symmetry.
Optical gain characterization of Perylene Red-doped PMMA for different pump configurations
Publisher: The Optical Society
Date: 24-12-2015
DOI: 10.1364/AO.55.000178
Spectroscopy of the Ã(B21)-X̃(A11) transition of jet-cooled fluorobenzene: Laser-induced fluorescence, dispersed fluorescence, and pathological Fermi resonances
Publisher: AIP Publishing
Date: 04-09-2007
DOI: 10.1063/1.2759931
Abstract: A detailed study of the S1(B21)-S0(A11) electronic transition of jet-cooled fluorobenzene has been carried out using laser-induced fluorescence and dispersed fluorescence (DF) spectroscopies. Analysis of over 40 single vibronic level DF spectra resulted in the assignment of 16 fundamental frequencies in the excited electronic state. Progressions in totally symmetric modes, particularly in the ring-breathing mode ν9, feature in both types of fluorescence spectrum. There is also significant activity in non-totally-symmetric modes, with activity in Franck-Condon (FC)-allowed overtones, FC-forbidden combinations induced by Duschinsky mixing, and symmetry-forbidden transitions induced by the same Herzberg-Teller vibronic coupling mechanism that induces the benzene S1-S0 transition. Fermi resonances (FRs) are extensive throughout the spectrum, especially in the important FC-active a1 modes. A consequence of these extensive FRs is that several important previous assignments are shown to be incorrect and have been reassigned here. Ab initio and density functional theory calculations have also been performed to support the experimental assignments.
Singlet Fission in Concentrated TIPS-Pentacene Solutions: The Role of Excimers and Aggregates
Publisher: American Chemical Society (ACS)
Date: 04-06-2021
DOI: 10.26434/CHEMRXIV.14727708.V1
Abstract: The exciton dynamics of 6,13-bis(triisopropylsilyl-ethynyl) pentacene is investigated to determine the role of excimer and aggregate formation in singlet fission in high concentration solutions. Photoluminescence spectra were measured by excitation with the evanescent wave in total internal reflection, in order to avoid reabsorption effects. The spectra over nearly two magnitudes of concentration were near identical, with no evidence for excimer emission. Time-correlated single-photon counting measurements confirm that the fluorescence lifetime shortens with concentration, and we obtain a bimolecular rate constant of $4\\times10^9$\\,M$^{-1}$s$^{-1}$ in chloroform. The observed rate constant grows at high concentrations. This effect is modelled in terms of the hard sphere radial distribution function. NMR measurements confirm that aggregation takes place with a binding constant of between 0.14 and 0.43M$^{-1}$. Transient absorption measurements are consistent with a diffusive encounter mechanism for singlet fission, with hints of more rapid singlet fission in aggregates at the highest concentration measured. These data show that excimers do not play the role of an emissive intermediate in exothermic singlet fission in solution, and that while aggregation occurs at higher concentrations, the mechanism of singlet fission remains dominated by diffusive encounters.
Localized electrons from diffusion Monte Carlo
Publisher: Elsevier BV
Date: 03-2004
Time-resolved Stark effect in rapidly varying fields
Publisher: Springer Science and Business Media LLC
Date: 04-2002
The dΠg3-cΣu+3 band system of C2
Publisher: AIP Publishing
Date: 04-12-2007
DOI: 10.1063/1.2805090
Abstract: A two-dimensional fluorescence (excitation/emission) spectrum of C2 produced in an acetylene discharge was used to identify and separate emission bands from the dΠg3←cΣu+3 and dΠg3←aΠu3 excitations. Rotationally resolved excitation spectra of the (4←1), (5←1), (5←2), and (7←3) bands in the dΠg3←cΣu+3 system of C2 were observed by laser-induced fluorescence spectroscopy. The molecular constants of each vibrational level, determined from rotational analysis, were used to calculate the spectroscopic constants of the cΣu+3 state. The principal molecular constants for the cΣu+3 state are Be=1.9319(19)cm−1, αe=0.01855(69)cm−1, ωe=2061.9cm−1, ωexe=14.84cm−1, and T0(c−a)=8662.925(3)cm−1. We report also the first experimental observations of dispersed fluorescence from the dΠg3 state to the cΣu+3 state, namely, dΠg3(v=3)→cΣu+3(v=0,1).
The exciton dynamics in tetracene thin films
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP52609G
Abstract: Tetracene thin films are investigated by time-resolved photoluminescence on picosecond to nanosecond time-scales. The picosecond luminescence decay dynamics is confirmed to be independent of temperature, but the nanosecond timescale luminescence dynamics is highly temperature dependent. This is interpretted in terms of motion along an intermolecular coordinate which couples the S1 state to the multiexciton (ME) state, arising from frustrated photodimerization, and giving rise to exciton dimming through adiabatic coupling. Dull excitons persist at low temperatures, but can thermally access separated triplet states at higher temperatures, quenching the delayed fluorescence. The effects of exciton density on both the picosecond and nanosecond luminescence dynamics are investigated, and a rate constant of (1.70 ± 0.08) × 10(-8) cm(3) s(-1) is determined for singlet-singlet annihilation.
Nanoporous Solid-State Sensitization of Triplet Fusion Upconversion
Publisher: American Chemical Society (ACS)
Date: 08-09-2023
H and D Attachment to Naphthalene: Spectra and Thermochemistry of Cold Gas-Phase 1-C10H9 and 1-C10H8D Radicals and Cations
Publisher: American Chemical Society (ACS)
Date: 19-03-2015
Abstract: Excitation spectra of the 1H-naphthalene (1-C10H9) and 1D-naphthalene (1-C10H8D) radicals, and their cations, are obtained by laser spectroscopy and mass spectrometry of a skimmed free-jet expansion following an electrical discharge. The spectra are assigned on the basis of density functional theory calculations. Isotopic shifts in origin transitions, vibrational frequencies and ionization energies were found to be well reproduced by (time-dependent) density functional theory. Absolute bond dissociation energies, ionization energies and proton affinities were calculated using high-level quantum chemical methods.
Sequence Structure Emission in the Red Rectangle Bands
Publisher: American Astronomical Society
Date: 03-2006
DOI: 10.1086/499260
Spectroscopy and thermochemistry of a jet-cooled open-shell polyene: 1,4-pentadienyl radical
Publisher: AIP Publishing
Date: 28-09-2011
DOI: 10.1063/1.3640475
Abstract: The 1,4-pentadienyl (vinylallyl) radical has been observed for the first time by optical spectroscopy. An excitation spectrum is recorded on m/z 67 by resonant two-color two-photon ionization spectroscopy. Several bands are observed with the origin transition identified at 19 449 cm−1. The spectrum is assigned by a comparison with ab initio frequencies calculated at the CASPT2/cc-pVTZ level of theory, with an accompanying Franck-Condon calculation of the excitation spectrum, including Dushinsky mixing. The b1 and a2 outer C–C bond torsional modes are calculated to halve in frequency upon electronic excitation, bringing about their appearance in the excitation spectrum. This can be readily understood by considering the torsional sensitivity of the frontier molecular orbital energies. High-level quantum chemical calculations of the radical stabilization energy, resulting in a value of nearly 120 kJ mol−1, provide quantitative confirmation that this radical is highly stabilized.
Excimer Formation in Carboxylic Acid-Functionalized Perylene Diimides Attached to Silicon Dioxide Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 24-01-2019
Time-resolved spectroscopy of the dynamic Stark effect
Publisher: IOP Publishing
Date: 23-02-2004
ac-Stark autocorrelator for ultrafast laser pulses
Publisher: Optica Publishing Group
Date: 08-2002
Gas phase electronic spectrum of the nitrogen terminated nanowire NC16N
Publisher: Elsevier BV
Date: 07-2004
Exciton Dissociation, Charge Transfer, and Exciton Trapping at the MoS2/Organic Semiconductor Interface
Publisher: American Chemical Society (ACS)
Date: 31-05-2023
Optical control of electronic state populations via the dynamic Stark effect
Publisher: Elsevier BV
Date: 06-2001
An add-on organic green-to-blue photon-upconversion layer for organic light emitting diodes
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7TC05649D
Abstract: Deep-blue emission from a green OLED is obtained by adding a thin gelled upconversion layer and additional dichroic filters.
Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission heterojunction devices
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8MH00853A
Abstract: Solar cells utilising heterojunctions between crystalline silicon and singlet fission materials are a new competitor to silicon tandem cells.
Excitation Spectra of the Jet-Cooled 4-Phenylbenzyl and 4-(4′-Methylphenyl)benzyl Radicals
Publisher: American Chemical Society (ACS)
Date: 25-10-2012
DOI: 10.1021/JP309003U
Abstract: The excitation spectra of jet-cooled 4-phenylbenzyl and 4-(4'-methylphenyl)benzyl radicals have been identified by a combination of resonant two-color two-photon ionization mass spectrometry and quantum chemical methods. Both radicals exhibit progressions in the biphenyl torsional mode, peaking near ν = 17. The lowest observed peak for 4-phenylbenzyl was observed at 18598 cm(-1) and is estimated to be the ν = 3 of the progression, while the lowest observed peak for the 4-(4'-methylphenyl)benzyl radical was observed at 18183 cm(-1) and is possibly the origin. The spectra are discussed and compared to other biphenyl and benzyl chromophores.
Singlet Fission in Concentrated TIPS-Pentacene Solutions: The Role of Excimers and Aggregates
Publisher: American Chemical Society (ACS)
Date: 04-06-2021
DOI: 10.26434/CHEMRXIV.14727708
Abstract: The exciton dynamics of 6,13-bis(triisopropylsilyl-ethynyl) pentacene is investigated to determine the role of excimer and aggregate formation in singlet fission in high concentration solutions. / br / Photoluminescence spectra were measured by excitation with the evanescent wave in total internal reflection, in order to avoid reabsorption effects. The spectra over nearly two magnitudes of concentration were near identical, with no evidence for excimer emission. Time-correlated single-photon counting measurements confirm that the fluorescence lifetime shortens with concentration, and we obtain a bimolecular rate constant of $4\\times10^9$\\,M$^{-1}$s$^{-1}$ in chloroform. The observed rate constant grows at high concentrations. This effect is modelled in terms of the hard sphere radial distribution function. / br / NMR measurements confirm that aggregation takes place with a binding constant of between 0.14 and 0.43M$^{-1}$. Transient absorption measurements are consistent with a diffusive encounter mechanism for singlet fission, with hints of more rapid singlet fission in aggregates at the highest concentration measured. / br / These data show that excimers do not play the role of an emissive intermediate in exothermic singlet fission in solution, and that while aggregation occurs at higher concentrations, the mechanism of singlet fission remains dominated by diffusive encounters. /
Resonance-Enhanced 2-Photon Ionization Scheme for C2 through a Newly Identified Band System: 43Πg–a3Πu
Publisher: American Chemical Society (ACS)
Date: 29-07-2015
Abstract: We report the observation of a new band system of C2, namely, the 4(3)Πg-a(3)Πu system. The bands, observed by resonant 2-photon ionization spectroscopy and time-of-flight mass spectrometry, were identified through a synergy of high-level ab initio computation and double-resonance spectroscopy. Two bands are firmly identified, 1-3 and 0-2, allowing the 4(3)Πg origin to be placed at 51496.44 cm(-1). The 4(3)Πg state is characterized as having a single bond, with a vibrational frequency of about 1268 cm(-1), and an equilibrium bond length of 1.57 Å. The state is predicted to exhibit a barrier to dissociation, with a rotational constant that unusually increases with vibrational excitation up to a maximum before decreasing at higher vibrational excitation. The new band system allows us to probe the a(3)Πu state of C2 through a straightforward 1 + 1 REMPI scheme.
Luminescent solar concentrators utilizing stimulated emission
Publisher: The Optical Society
Date: 16-02-2016
DOI: 10.1364/OE.24.00A497
Efficiency Enhancement of Organic and Thin-Film Silicon Solar Cells with Photochemical Upconversion
Publisher: American Chemical Society (ACS)
Date: 23-10-2012
DOI: 10.1021/JP309636M
Improved optical confinement in ambipolar field-effect transistors toward electrical injection organic lasers
Publisher: AIP Publishing
Date: 18-10-2021
DOI: 10.1063/5.0063336
Abstract: Increasing optical confinement is critical to lowering laser thresholds and increasing modal gain in semiconductor lasers. Here, mode-solver calculations are used to demonstrate that improvements to optical confinement are possible in organic field-effect transistor geometries by using high refractive index cladding layers. Optical experiments show that the proposed structure increases the efficiency of lified spontaneous emission (ASE) and lowers ASE thresholds without incurring additional losses. The results suggest that the structure can be used to improve optical confinement for both optically pumped and electrical injection organic lasers where thin, low refractive index active materials are required.
Structure of the Naphthalene Dimer from Rare Gas Tagging
Publisher: American Chemical Society (ACS)
Date: 21-04-2007
DOI: 10.1021/JP0687504
Abstract: Excitation spectra of naphthalene dimer-argonn (n = 1-3) clusters are obtained by resonance enhanced multiphoton ionization time-of-flight mass spectroscopy. The spectra are generally independent of the number of attached argon atoms and reveal sharp structures which are fitted by superimposing independent monomer spectra. It is concluded that the rare-gas tagging technique reveals the presence of a T-shaped naphthalene dimer chromophore in the molecular beam.
Quantum chemical study and experimental observation of a new band system of C2, e Π3g−c Σ3u+
Publisher: AIP Publishing
Date: 22-07-2009
DOI: 10.1063/1.3175013
Abstract: A new band system of C2, e Π3g−c Σ3u+ was studied by ab initio quantum chemical and experimental methods. The calculations were carried out at the multireference configuration interaction level of theory with Davidson’s correction using aug-cc-pV6Z basis set and include core and core-valence correlation as well as relativistic corrections computed with aug-cc-pCVQZ and cc-pVQZ bases, respectively. The vibrational energies and rotational constants of the upper e Π3g state were calculated from the computed ab initio potential energy curve. The ab initio results indicate that the electronic transition moment of the e Π3g−c Σ3u+ system is approximately one-half that of the Fox–Herzberg e Π3g−a Π3u system. Franck–Condon factors were calculated for both systems and used to guide experiments aimed at discovering the e Π3g−c Σ3u+ system. The e Π3g(v′=4)−c Σ3u+(v″=3) band of jet-cooled C2 was successfully observed by laser-induced fluorescence spectroscopy by monitoring the ensuing e Π3g−a Π3u emission.
Plasmonic effects on CO2 reduction over bimetallic Ni-Au catalysts
Publisher: Elsevier BV
Date: 02-2019
Photochemical Upconversion: The Primacy of Kinetics
Publisher: American Chemical Society (ACS)
Date: 12-11-2014
DOI: 10.1021/JZ501799M
Abstract: Incoherent photochemical upconversion is a process by which low-energy light can be converted into a higher-energy form with promising applications in solar energy conversion and storage, photocatalysis, biological imaging, and photochemical drug activation. Despite intensive research in recent years, there remains an underappreciation of the chemical kinetics that controls the efficiency of the upconversion process. Here, we provide a brief overview of research into photochemical upconversion and provide a tutorial to guide the design of efficient upconversion compositions. We further provide our perspective on where this area of research is heading and how very efficient systems will be developed.
Endothermic singlet fission is hindered by excimer formation
Publisher: Springer Science and Business Media LLC
Date: 22-01-2018
DOI: 10.1038/NCHEM.2926
Abstract: Singlet fission is a process whereby two triplet excitons can be produced from one photon, potentially increasing the efficiency of photovoltaic devices. Endothermic singlet fission is desired for a maximum energy-conversion efficiency, and such systems have been considered to form an excimer-like state with multiexcitonic character prior to the appearance of triplets. However, the role of the excimer as an intermediate has, until now, been unclear. Here we show, using 5,12-bis((triisopropylsilyl)ethynyl)tetracene in solution as a prototypical ex le, that, rather than acting as an intermediate, the excimer serves to trap excited states to the detriment of singlet-fission yield. We clearly demonstrate that singlet fission and its conjugate process, triplet-triplet annihilation, occur at a longer intermolecular distance than an excimer intermediate would impute. These results establish that an endothermic singlet-fission material must be designed to avoid excimer formation, thus allowing singlet fission to reach its full potential in enhancing photovoltaic energy conversion.
Future and challenges for hybrid upconversion nanosystems
Publisher: Springer Science and Business Media LLC
Date: 28-10-2019
Deuteration of Perylene Enhances Photochemical Upconversion Efficiency
Publisher: American Chemical Society (ACS)
Date: 22-07-2015
DOI: 10.1021/ACS.JPCLETT.5B01271
Abstract: Photochemical upconversion via triplet-triplet annihilation is a promising technology for improving the efficiency of photovoltaic devices. Previous studies have shown that the efficiency of upconversion depends largely on two rate constants intrinsic to the emitting species. Here, we report that one of these rate constants can be altered by deuteration, leading to enhanced upconversion efficiency. For perylene, deuteration decreases the first order decay rate constant by 16 ± 9% at 298 K, which increases the linear upconversion response by 45 ± 21% in the low excitation regime.
The 15Πg state of C2
Publisher: AIP Publishing
Date: 14-06-2011
DOI: 10.1063/1.3599933
Abstract: We report ab initio spectroscopic constants for the recently identified 15Πg state of C2 [P. Bornhauser, Y. Sych, G. Knopp, T. Gerber, and P. P. Radi, J. Chem. Phys. 134, 044302 (2011)]. The calculations are performed at the multi-reference configuration interaction level of theory with Davidson's correction using aug-cc-pV6Z basis sets and include core-valence correlation and relativistic corrections obtained with quadruple-zeta bases. Such treatment accurately reproduces the experimentally observed constants of the a3Πu and other states. Thus, we expect our calculated ωe value for the 15Πg state to be within a few cm−1, and rotational constants to be within 0.1% of experiment. Agreement with available spectroscopic data is excellent, with the calculations strongly suggesting that the 15Πg vibrational level observed by Bornhauser et al. is v = 0.
Optical analysis of an integrated solar cell and a photon up converter, providing guidance for future device engineering efforts
Publisher: AIP Publishing
Date: 16-11-2021
DOI: 10.1063/5.0072034
Abstract: To date, a number of photon up-conversion (UC) systems with high quantum efficiencies have been demonstrated, including at non-concentrated solar illumination intensities. These are, however, yet to be successfully combined with photovoltaic devices in order to provide substantial increases in photocurrent, as compared with devices without UC. In the present work, we perform simple calculations, based on the optical properties of an UC + solar cell system, specifically a dye-sensitized solar cell and sensitized-triplet-triplet annihilation based UC system, in line with our previous experimentally realized proof-of-concept devices. This model is then used to more specifically identify the limitations and losses, thereby providing a pathway toward improvements, based on either real or hypothetical materials. This model highlights that only a fraction of the benefit may be realized without substantial improvements being made in terms of various transmission losses, coupled with the fact that UC emission typically scales quadratically in this flux regime. The model presented can help identify where research efforts should be focused as well as where there may be little utility, with these lessons also being valuable in the future as even more efficient UC systems are developed. Furthermore, a spreadsheet is provided in the supplementary material to assist other researchers in their efforts.
Velocity Map Imaging Spectroscopy of the Dipole-Bound State of CH2CN–: Implications for the Diffuse Interstellar Bands
Publisher: American Chemical Society (ACS)
Date: 02-11-2021
DOI: 10.1021/JACS.1C08762
Singlet and Triplet Exciton Dynamics of Violanthrone
Publisher: American Chemical Society (ACS)
Date: 06-10-2021
Two-Dimensional Fluorescence (Excitation/Emission) Spectroscopy as a Probe of Complex Chemical Environments
Publisher: American Chemical Society (ACS)
Date: 21-10-2006
DOI: 10.1021/JP064411Z
Abstract: We report a new application of fluorescence spectroscopy for the identification and characterization of chemical species in complex environments. Simultaneous collection of a dispersed fluorescence spectrum for every step of the laser wavelength results in a two-dimensional spectrum of emission versus excitation wavelengths. This two-dimensional fluorescence (2DF) spectrum yields quick and intuitive assignments of a multitude of peaks in the separate fluorescence excitation and dispersed fluorescence spectra as belonging to the same species. We demonstrate the technique with the measurement of 2DF spectra of a discharge of dilute benzene into a supersonic free jet. A multitude of rovibronic bands due to the C(2) Swan and C(3) comet bands are immediately apparent and even unreported bands can be assigned intuituvely. Custom software filters are employed to enhance or reject emission from one or the other carrier to obtain excitation spectra arising from purely one carrier, or even a specific spectral component of a single carrier. The very characteristic 2DF fingerprints of C(2) and C(3) permit identification of another unidentified species in the discharge that absorbs at 476 nm, coincident with one of the diffuse interstellar bands.
Energy Transfer between Perylene Diimide Based Ligands and Cesium Lead Bromide Perovskite Nanocrystals
Publisher: American Chemical Society (ACS)
Date: 15-01-2020
A theoretical treatment of the absorption spectra of all-benzenoid hydrocarbons
Publisher: Oxford University Press (OUP)
Date: 09-2006
Energy transfer in pendant perylene diimide copolymers
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6TC02555B
Abstract: We report the synthesis and characterisation of novel copolymers comprising asymmetric perylene diimide acrylate monomers.
E-field dependence of the ac Stark effect probed by a bichromatic laser field
Publisher: IOP Publishing
Date: 09-05-2002
Hydroxyl Addition to Aromatic Alkenes: Resonance-Stabilized Radical Intermediates
Publisher: American Chemical Society (ACS)
Date: 20-07-2012
DOI: 10.1021/JP304875R
Abstract: The spectra of 1-indanyl-based resonance-stabilized radicals containing a hydroxyl group are identified in an electrical discharge containing indene and its alkylated derivatives. It is argued that such species form by addition of a discharge-nascent hydroxyl radical, formed from trace water, to the π bond on the five-membered ring of the parent molecule. The spectral carriers are identified by analysis of their excitation and emission spectra guided by the results from quantum chemical calculations. All three hydroxylated radicals are found to exhibit origin bands in the 21300 cm(-1) region: the 2-hydroxy-indan-1-yl radical at 21364 cm(-1), the 2-hydroxy-2-methyl-indan-1-yl radical at 21337 cm(-1), and the 2-ethyl-2-hydroxy-indan-1-yl radical exhibiting two origins of similar intensity at 21287 and 21335 cm(-1).
The efficiency limit of solar cells with molecular absorbers: A master equation approach
Publisher: AIP Publishing
Date: 15-12-2010
DOI: 10.1063/1.3517826
Abstract: A master equation approach to the limiting efficiencies of solar cells with molecular absorbers is presented. A number of model absorbers are analyzed that possess identical absorption spectra, but with differing numbers of electronic excited states. The Shockley–Queisser limit is reproduced for a molecule resembling a semiconductor, with an infinity of electronic levels in the excited state manifold. However, when only a few electronic states contribute to the absorption spectrum, the limiting efficiency is reduced. In the extreme case, where only a single electronic excited state participates in the absorption spectrum, the efficiency limit is 28.9%. At high energy thresholds, built-in thermal up-conversion results in solar cells with efficiencies exceeding the Shockley–Queisser curve. The analysis is applicable to any single threshold photovoltaic device, including those based on semiconductor, polymer, and small molecule absorbers.
Excitation spectra of large jet-cooled polycyclic aromatic hydrocarbon radicals: 9-Anthracenylmethyl (C15 H11 ) and 1-pyrenylmethyl (C17 H11 )
Publisher: American Chemical Society (ACS)
Date: 17-10-2013
DOI: 10.1021/JP4088833
Abstract: The 9-anthracenylmethyl (C15H11) and 1-pyrenylmethyl (C17H11) radicals were identified by a combination of mass-resolved laser spectroscopy of a jet-cooled electrical discharge and quantum chemical methods. The 9-anthracenylmethyl radical was found to exhibit an origin band at 13757 cm(-1), with vibrational structure observed in a1 modes, and even quanta of b1 and a2 modes. The 1-pyrenylmethyl radical was found to exhibit an origin band at 13,417 cm(-1), with a more complex vibrational structure as compared to 9-anthracenylmethyl, on account of its lower symmetry and larger size. The origin bands of these species were predicted to within 250 cm(-1) by fitting a linear relationship between observed origin wavelengths of similar chromophores and the calculated TD-B3LYP transition energies. A refined fit including the title radicals provides estimated absorption energies for the larger 2-perylenylmethyl and 6-anthanthrenylmethyl species of 1.44 and 1.41 eV, respectively, with an estimated error of 30 meV.
Luminescent solar concentrator improvement by stimulated emission
Publisher: SPIE
Date: 22-12-2015
DOI: 10.1117/12.2202787
Efficient up-conversion by triplet-triplet annihilation
Publisher: IOP Publishing
Date: 09-2009
On the Quantum Yield of Photon Upconversion via Triplet–Triplet Annihilation
Publisher: American Chemical Society (ACS)
Date: 22-06-2020
Oxygen-Enhanced Upconversion of near Infrared Light from Below the Silicon Band Gap
Publisher: American Chemical Society (ACS)
Date: 13-03-2019
DOI: 10.26434/CHEMRXIV.7834838.V1
Abstract: Here we demonstrate an upconversion composition using semiconductor nanocrystal sensitizers that employs molecular triplet states below the singlet oxygen energy. We show that, contrary to the usual expectation, the admission of oxygen enhances the intensity of upconverted light and significantly speeds up the photochemical processes involved. Further, we demonstrate photochemical upconversion from below the silicon band gap in the presence of oxygen.
Kinetic insight into bimolecular upconversion: experiment and simulation
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3RA46953K
Abstract: Direct observation of triplet energy transfer from sensitiser to emitter is modelled and provides comprehensive description of bimolecular upconversion.
The spectroscopy and thermochemistry of phenylallyl radical chromophores
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1SC00247C
Action spectrum experiment for the measurement of incoherent photon upconversion efficiency under sun-like excitation
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4RA08706B
Abstract: A dual beam experiment accurately determines the efficiency of red-to-yellow upconversion under one-sun conditions.
Oscillator strengths and radiative lifetimes for C2: Swan, Ballik-Ramsay, Phillips, and dΠg3←cΣu+3 systems
Publisher: AIP Publishing
Date: 22-02-2007
DOI: 10.1063/1.2436879
Abstract: High level ab initio calculations, using multireference configuration interaction (MRCI) techniques, have been carried out to investigate the spectroscopic properties of the singlet AΠu1←XΣg+1 Phillips, the triplet dΠg3←aΣu3 Swan, the bΣg−3←aΠu3 Ballik-Ramsay, and the dΠg3←cΣu+3 transitions of C2. The MRCI expansions are based on full-valence complete active space self-consistent-field reference states and utilize the aug-cc-pV6Z basis set to resolve valence electron correlation. Core and core-valence correlations and scalar relativistic energy corrections were also incorporated in the computed potential energy surfaces. Nonadiabatic and spin-orbit effects were explored and found to be of negligible importance in the calculations. Harmonic frequencies and rotational constants are typically within 0.1% of experiment. The calculated radiative lifetimes compare very well with the available experimental data. Oscillator strengths are reported for all systems: fv′v″, where 0⩽v⩽5.
The electronic spectroscopy of resonance-stabilised hydrocarbon radicals
Publisher: Informa UK Limited
Date: 02-04-2016
Unraveling the Ã1B1 ← X̃1A1 Spectrum of CCl2: The Renner−Teller Effect, Barrier to Linearity, and Vibrational Analysis Using an Effective Polyad
Publisher: American Chemical Society (ACS)
Date: 17-10-2008
DOI: 10.1021/JP806944Q
Abstract: We report studies aimed at unraveling the complicated structure of the CCl 2 A (1)B 1 <-- X (1)A 1 system. We have remeasured the fluorescence excitation spectrum from approximately 17,500 to 24,000 cm (-1) and report the term energies and A rotational constants of many new bands for both major isotopologues (C (35)Cl 2, C (35)Cl (37)Cl). We fit the observed term energies to a polyad effective Hamiltonian model and demonstrate that a single resonance term accounts for much of the observed mixing, which begins approximately 1300 cm (-1) above the vibrationless level of the A (1)B 1 state. The derived A (1)B 1 vibrational parameters are in excellent agreement with ab initio predictions, and the mixing coefficients deduced from the polyad model fit are in close agreement with those derived from direct fits of single vibronic level (SVL) emission intensities. The approach to linearity and thus the Renner-Teller (RT) intersection is probed through the energy dependence of the A rotational constant and fluorescence lifetime measurements, which indicate a barrier height above the vibrationless level of the X (1)A 1 state of approximately 23,000-23,500 cm (-1), in excellent agreement with ab initio theory.
Singlet and Triplet Exciton Dynamics of Violanthrone
Publisher: American Chemical Society (ACS)
Date: 30-03-2021
DOI: 10.26434/CHEMRXIV.14331737
Abstract: The exciton dynamics of violanthrone-79 are investigated in solution and in the solid / state. In solution, the photo-prepared singlet is found to exhibit a strong ground-state bleach / and stimulated emission feature, but when sensitized in its triplet state, exhibits only a narrow / and weak ground-state bleach. As supported by density functional theory calculations, / this is explained by the triplet state having absorptions in the same region, with a similar / oscillator strength, as the ground state molecule. In solid films, the excited singlet is / found to survive only 100 ps, giving way to a long-lived transient absorption spectrum with / characteristics reminiscent of the triplet in solution. This is interpreted in terms of singlet / fission in the solid film. /
Two-photon triplet-triplet annihilation upconversion for photovoltaics
Publisher: IEEE
Date: 06-2011
Identification of the Jet-Cooled 1-Indanyl Radical by Electronic Spectroscopy
Publisher: American Chemical Society (ACS)
Date: 09-2009
DOI: 10.1021/JP905831M
Abstract: The electronic spectrum of the jet-cooled 1-indanyl radical has been identified in the products of a hydrocarbon discharge in argon. Electronic excitation spectra were observed in the region 20800-22600 cm(-1) by resonant two-color two-photon ionization and laser-induced fluorescence spectroscopies. In addition to the new spectrum at m/z = 117, the spectrum of 1-phenylpropargyl was also observed strongly, as was an unidentified spectrum carried by m/z = 133. The origin band of the 1-indanyl A2A''-X2A'' band system was observed at 21159 cm(-1) with the ionization potential of the radical experimentally determined to be 6.578 +/- 0.001 eV from a photoionization efficiency spectrum. Single vibronic level fluorescence was dispersed to determine the ground state vibrational frequencies that were utilized to confirm the identity of the radical in comparison with quantum chemical calculations. The calculated ground state frequencies and ionization potential, along with a calculated dispersed fluorescence spectrum of the origin band for the 1-indanyl radical, all provide a positive chemical identification.
Improving the light-harvesting of amorphous silicon solar cells with photochemical upconversion
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2EE21136J
The dynamics of CO production from the photolysis of acetone across the whole S1 ← S absorption spectrum: Roaming and triple fragmentation pathways
Publisher: AIP Publishing
Date: 03-2022
DOI: 10.1063/5.0080904
Abstract: The unimolecular photodissociation dynamics of acetone spanning the entire S1 ← S0 absorption spectrum have been reinvestigated, with a focus on mechanisms that produce CO. At excitation wavelengths of λ & 305.8 nm, all photoproducts are formed on the S0 state after internal conversion. A roaming mechanism forming C2H6 + CO is active in the window λ = 311.2–305.8 nm. From λ = 305.8 to 262 nm, little or no CO is produced with the photochemistry dominated by the Norrish-type I C–C bond cleavage on the lowest excited triplet state, T1. At higher energy (λ & 262 nm), an increasing fraction of CH3CO radicals from the primary reaction have sufficient internal energy to spontaneously decompose to CH3 + CO. A new model is presented to account for the kinetic energy distribution of the secondary CH3 radical, allowing us to determine the height of the energetic barrier to CH3CO decomposition as 68 ± 4 kJ mol−1, which lies midway between previous measurements. The fraction of CO from triple fragmentation rises smoothly from 260 to 248 nm. We see no evidence of the return of roaming, or any other S0 reaction, in this higher energy region of the first electronic absorption band.
PAH Growth in Flames and Space: Formation of the Phenalenyl Radical
Publisher: American Chemical Society (ACS)
Date: 22-12-2021
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are intermediates in the formation of soot particles and interstellar grains. However, their formation mechanisms in combustion and interstellar environments are not fully understood. The production of tricyclic PAHs and, in particular, the conversion of a PAH containing a five-membered ring to one with a six-membered ring are of interest to explain PAH abundances in combustion processes. In the present work, resonant ionization mass spectrometry in conjunction with isotopic labeling is used to investigate the formation of the phenalenyl radical from acenaphthylene and methane in an electrical discharge. We show that in this environment the CH cycloaddition mechanism converts a five-membered ring to a six-membered ring. This mechanism can occur in tandem with other PAH formation mechanisms such as hydrogen abstraction/acetylene addition (HACA) to produce larger PAHs in flames and the interstellar medium.
Spectral dependence of direct and trap-mediated recombination processes in lead halide perovskites using time resolved microwave conductivity
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5CP07360J
Abstract: Elucidating the decay mechanisms of photoexcited charge carriers is key to improving the efficiency of solar cells based on organo-lead halide perovskites.
Diabatic Valence-Hole States in the C2 Molecule: “Putting Humpty Dumpty Together Again”
Publisher: American Chemical Society (ACS)
Date: 11-05-2022
Abstract: Despite the long history of spectroscopic studies of the C
Power Dependence of the Magnetic Field Effect on Triplet Fusion: A Quantitative Model
Publisher: American Chemical Society (ACS)
Date: 15-05-2023
First observation of the 3Πg3 state of C2: Born-Oppenheimer breakdown
Publisher: AIP Publishing
Date: 04-04-2017
DOI: 10.1063/1.4979293
Abstract: The 33Πg state of the dicarbon molecule, C2, has been identified for the first time by a combination of resonant ionization spectroscopy, mass spectrometry, and high-level ab initio quantum chemical calculations. This marks the discovery of the final valence triplet state of C2 spectroscopically accessible from the lowest triplet state. It is found to be vibronically coupled to the recently discovered 43Πg state, necessitating vibronic calculations beyond the Born-Oppenheimer approximation to reconcile calculated rotational constants with observations. The 33Πg state of C2 is observed to have a much shorter fluorescence lifetime than expected, possibly pointing to predissociation by coupling to the unbound d3Πg state.
High efficiency deep red to yellow photochemical upconversion under solar irradiance
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1EE02197D
Abstract: Photochemical upconversion is performed using ch ion sensitizers and annihilators to achieve high efficiencies under one sun.
Hot Carrier Cooling in In0.17Ga0.83As/GaAs0.80P0.20 Multiple Quantum Wells: The Effect of Barrier Thickness
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2016
Synthesis and Ultrafast Excited-State Dynamics of Zinc and Palladium Triply Fused Diporphyrins
Publisher: American Chemical Society (ACS)
Date: 23-07-2012
DOI: 10.1021/JP3043895
Abstract: We report the synthesis and ultrafast excited-state dynamics of two new meso-meso, β-β, β-β triply fused diporphyrins, Zn-3DP and Pd-3DP. Both compounds were found to have short excited-state lifetimes: Zn-3DP possessed an average S1 lifetime of 14 ps before nonradiative deactivation to the ground state, whereas Pd-3DP displayed a longer average S1 lifetime of 18 ps before crossing to the T1 state, which itself possessed a very short triplet lifetime of 1.7 ns. The excited-state dynamics of Zn-3DP, compared to similar zinc(II) diporphyrins reported in the literature, suggests that a conical intersection of the S1 and S0 potential energy surfaces plays a major role as a deactivation pathway of these molecules. Furthermore, the short triplet lifetime of Pd-3DP, compared to other diporphyrins that also exploit the intramolecular heavy atom effect, reveals that the position of the heavy atom within the diporphyrin framework influences the strength of spin-orbit coupling. The implications for employing triply fused diporphyrins as NIR-absorbing triplet sensitizers are discussed.
InGaAs/GaAsP quantum wells for hot carrier solar cells
Publisher: SPIE
Date: 09-02-2012
DOI: 10.1117/12.910581
Thermodynamic limit of exciton fission solar cell efficiency
Publisher: American Chemical Society (ACS)
Date: 13-09-2012
DOI: 10.1021/JZ301069U
Organic polariton lasing with molecularly isolated perylene diimides
Publisher: AIP Publishing
Date: 27-07-2020
DOI: 10.1063/5.0012461
Abstract: A dye immersed in a polymer matrix represents a promising material class for organic polariton lasers. While polariton condensation has been established for boron-dipyrromethene blends, it has yet to be extended to other small dye blends. Here, we demonstrate polariton lasing in a molecularly isolated perylene diimide immersed in polystyrene. The emission exhibits threshold behavior, strong directionality, and slight blueshifting of organic polariton systems. We expect that continuous exploration of new dyes will allow improved performance in organic polariton lasing.
Singlet fission and tandem solar cells reduce thermal degradation and enhance lifespan
Publisher: Wiley
Date: 05-05-2021
DOI: 10.1002/PIP.3405
Abstract: The economic value of a photovoltaic installation depends upon both its lifespan and power conversion efficiency. Progress toward the latter includes mechanisms to circumvent the Shockley‐Queisser limit, such as tandem designs and multiple exciton generation (MEG). Here we explain how both silicon tandem and MEG‐enhanced silicon cell architectures result in lower cell operating temperatures, increasing the device lifetime compared to standard c‐Si cells. Also demonstrated are further advantages from MEG enhanced silicon cells: (i) the device architecture can completely circumvent the need for current‐matching and (ii) upon degradation, tetracene, a candidate singlet fission (a form of MEG) material, is transparent to the solar spectrum. The combination of (i) and (ii) mean that the primary silicon device will continue to operate with reasonable efficiency even if the singlet fission layer degrades. The lifespan advantages of singlet fission enhanced silicon cells, from a module perspective, are compared favorably alongside the highly regarded perovskite/silicon tandem and conventional c‐Si modules.
Line strengths and updated molecular constants for the C2 Swan system
Publisher: Elsevier BV
Date: 07-2013
Electronic transitions of molecules: vibrating Lewis structures
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9SC02534K
Abstract: A partitioning of the wavefunction into tiles allows electronic excitations to be viewed as electron vibrations.
ac Stark shifts in Rydberg NO levels induced by intense laser pulses
Publisher: American Physical Society (APS)
Date: 16-06-2000
Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light
Publisher: MyJove Corporation
Date: 12-09-2014
DOI: 10.3791/52028
Electronic Transitions of Molecules: Vibrating Lewis Structures
Publisher: American Chemical Society (ACS)
Date: 21-03-2019
DOI: 10.26434/CHEMRXIV.7871921.V1
Abstract: In this work we demonstrate a simple and intuitive description of electronic resonances in terms of localized electron vibrations. By partitioning the 3N-dimensional space of a many-electron wavefunction into hyper-regions related by permutation symmetry, chemical structures naturally result which correspond closely to Lewis structures, with identifiable single and double bonds, and lone pairs. Here we demonstrate how this picture of electronic structure develops upon the admixture of electronic wavefunctions, in the spirit of coherent electronic transitions. We show that pi-pi* transitions correspond to double-bonding electrons oscillating along the bond axis, and n-pi* transitions reveal lone-pairs vibrating out of plane. In butadiene and hexatriene, the double-bond oscillations combine with in- and out-of-phase combinations, revealing the correspondence between electronic transitions, molecular normal mode vibrations, and molecular plasmonics. This analysis allows electronic excitations to be described by building upon ground state electronic structures, without the need for molecular orbitals.
Using Atomic Orbitals and Kinesthetic Learning To Authentically Derive Molecular Stretching Vibrations
Publisher: American Chemical Society (ACS)
Date: 28-05-2013
DOI: 10.1021/ED300045Q
Photochemical upconversion of near-infrared light from below the silicon bandgap
Publisher: Springer Science and Business Media LLC
Date: 20-07-2020
Photochemical Upconversion in Solution: The Role of Oxygen and Magnetic Field Response
Publisher: American Chemical Society (ACS)
Date: 08-02-2023
Oxygen-Enhanced Upconversion of near Infrared Light from Below the Silicon Band Gap
Publisher: American Chemical Society (ACS)
Date: 13-03-2019
DOI: 10.26434/CHEMRXIV.7834838
Abstract: Here we demonstrate an upconversion composition using semiconductor nanocrystal sensitizers that employs molecular triplet states below the singlet oxygen energy. We show that, contrary to the usual expectation, the admission of oxygen enhances the intensity of upconverted light and significantly speeds up the photochemical processes involved. Further, we demonstrate photochemical upconversion from below the silicon band gap in the presence of oxygen. /
Increased upconversion performance for thin film solar cells: a trimolecular composition
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5SC03215F
Abstract: A dual-emitter upconvertor is applied to thin-film solar cells for the first time, generating record figures of merit.
Photophysical properties of a new series of water soluble iridium bisterpyridine complexes functionalised at the 4′ position
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0DT01317J
Abstract: Four new hetero- and homo-leptic iridium(III) bisterpyridine complexes have been prepared which incorporate aniline (tpy-φ-NH(2)), benzoic acid (tpy-φ-COOH), and benzyl alcohol (tpy-φ-CH(2)OH) substituents at the 4' positions of the tpy ligands (tpy = 2,2':6',2''-terpyridine, φ = phenylene). The electrochemical behaviour and ground and excited state spectroscopic properties of the complexes are reported, and the X-ray crystal structures of a homoleptic benzyl alcohol [Ir(tpy-φ-CH(2)OH)(2)](PF(6))(3), homoleptic aniline [Ir(tpy-φ-NH(2))(2)](PF(6))(3), and heteroleptic benzyl alcohol/aniline substituted complex [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))](PF(6))(3) have been solved. Complexes with aniline substituents were found to display absorption bands at around 430 nm corresponding to intraligand charge transfer (ILCT) that are sensitive to changes in solvent and pH. Strong emission in the visible region involving the ILCT state is observed in two of the complexes (Φ(e) = 0.7% and 2.6%) in acetonitrile. In the heteroleptic aniline/benzyl alcohol complex the Stokes shift is shown to be linearly related to solvent polarisability according to the Lippert equation, but only for solvents with weak hydrogen bonding interactions. Additionally, in water, emission from the ILCT state is quenched and only weak ligand centred (LC) emission is observed. The long lifetimes and quantum yields of these complexes make them interesting candidates for probes in sensing applications, especially [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))(2)](PF(6))(3) due to its unusual sensitivity to the solvent environment.
Chemical bonding motifs from a tiling of the many-electron wavefunction
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CP01188H
Abstract: A method is presented to partition the 3 N -dimensional space of a many-electron wavefunction into hyper-regions related by permutation symmetry.
PAH growth in flames and space: Formation of phenalenyl radical
Publisher: Cambridge University Press (CUP)
Date: 03-09-2021
DOI: 10.33774/CHEMRXIV-2021-P9XR8
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are intermediates in the formation of soot particles and interstellar grains. However, their formation mechanisms in combustion and interstellar environments are not fully understood. The production of tricyclic PAHs and, in particular, the conversion of a PAH containing a five-membered ring to one with a six-membered ring is of interest to explain PAH abundances in combustion processes. In the present work, resonant ionization mass spectrometry in conjunction with isotopic labelling is used to investigate the formation of the phenalenyl radical from acenaphthylene and methane in an electrical discharge. We show that in this environment, the CH cycloaddition mechanism converts a five-membered ring to a six-membered ring. This mechanism can occur in tandem with other PAH formation mechanisms such as hydrogen abstraction/ acetylene addition (HACA) to produce larger PAHs in flames and the interstellar medium.
The electronic structure of benzene from a tiling of the correlated 126-dimensional wavefunction
Publisher: Springer Science and Business Media LLC
Date: 05-03-2020
DOI: 10.1038/S41467-020-15039-9
Abstract: The electronic structure of benzene is a battleground for competing viewpoints of electronic structure, with valence bond theory localising electrons within superimposed resonance structures, and molecular orbital theory describing delocalised electrons. But, the interpretation of electronic structure in terms of orbitals ignores that the wavefunction is anti-symmetric upon interchange of like-spins. Furthermore, molecular orbitals do not provide an intuitive description of electron correlation. Here we show that the 126-dimensional electronic wavefunction of benzene can be partitioned into tiles related by permutation of like-spins. Employing correlated wavefunctions, these tiles are projected onto the three dimensions of each electron to reveal the superposition of Kekulé structures. But, opposing spins favour the occupancy of alternate Kekulé structures. This result succinctly describes the principal effect of electron correlation in benzene and underlines that electrons will not be spatially paired when it is energetically advantageous to avoid one another.
Charting a course for chemistry
Publisher: Springer Science and Business Media LLC
Date: 22-03-2019
Luminescent hyperbranched polymers: Combining thiol-yne chemistry with gold-mediated C-H bond activation
Publisher: American Chemical Society (ACS)
Date: 11-02-2011
DOI: 10.1021/OM200103F
Large, Tunable, and Reversible pH Changes by Merocyanine Photoacids
Publisher: American Chemical Society (ACS)
Date: 30-11-2021
DOI: 10.1021/JACS.1C08810
Abstract: Molecular photoswitches capable of generating precise pH changes will allow pH-dependent processes to be controlled remotely and noninvasively with light. We introduce a series of new merocyanine photoswitches, which deliver reversible bulk pH changes up to 3.2 pH units (pH 6.5 to pH 3.3) upon irradiation with 450 nm light, displaying tunable and predictable timescales for thermal recovery. We present models to show that the key parameters for optimizing the bulk pH changes are measurable: the solubility of the photoswitch, the acidity of the merocyanine form, the thermal equilibrium position between the spiropyran and the merocyanine isomers, and the increased acidity under visible light irradiation. Using ultrafast transient absorption spectroscopy, we determined the quantum yields for the ring-closing reaction and found that the lifetimes of the transient
Photochemical upconversion is suppressed by high concentrations of molecular sensitizers
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CP02650E
Abstract: High concentrations of molecular sensitizer shorten emitter triplet lifetimes and lead to lower upconversion efficiency.
Singlet Oxygen Mediated Photochemical Upconversion of NIR Light
Publisher: American Chemical Society (ACS)
Date: 08-04-2011
DOI: 10.1021/JZ200270W
Photodissociation of dicarbon: How nature breaks an unusual multiple bond
Publisher: Proceedings of the National Academy of Sciences
Date: 20-12-2021
Abstract: It has long been observed that the coma of a comet is often green while its tail is not. While the explanation for this must be that the molecules responsible for the green emission, C 2 , are photodissociated, the mechanism was, until now, unknown. We have observed the photodissociation of C 2 in the laboratory for the first time and, in doing so, have determined its bond dissociation energy with unprecedented precision. Invoking the observed mechanism, the calculated lifetime of cometary C 2 is found to be consistent with astronomical observations.
Aliphatic hydrocarbon content of interstellar dust
Publisher: Oxford University Press (OUP)
Date: 18-06-2018
Ab initio potential energy surface and vibrational frequencies of Ã(1A″) HCF
Publisher: Elsevier BV
Date: 07-1998
Measured power conversion efficiencies of bifacial luminescent solar concentrator photovoltaic devices of the mosaic series
Publisher: Wiley
Date: 28-02-2022
DOI: 10.1002/PIP.3546
Abstract: The optical and electrical performances of varied configurations of visually attractive mosaic cubical luminescent solar concentrator photovoltaic (LSC PV) devices have been measured. These new designs of LSC PV devices consist of four cubical lightguides containing commercially available fluorophores with edge‐ and bottom‐mounted silicon solar cells. The 1 cm 3 cubical component LSC PVs are made of poly (methyl methacrylate) (PMMA) doped by dyes from 10 to 150 ppm. The lightguides are covered with bifacial silicon solar cells at their edges and/or bottom and connected in series or parallel, depending on the device configuration. In total, 19 different configurations of mosaic LSC PV devices have been experimentally evaluated in this study.
Aliphatic hydrocarbon content of interstellar dust
Publisher: Cambridge University Press (CUP)
Date: 04-2019
DOI: 10.1017/S1743921320000691
Abstract: The mid-IR spectrum of the interstellar medium contains both aromatic and aliphatic hydrocarbon features. These are generally attributed to carbonaceous dust. The aliphatic component is of particular interest because it produces a significant 3.4 μ m absorption feature. The optical depth of this feature is related to the number and type of aliphatic carbon C–H bonds in the line of sight. It is possible to estimate the column density of aliphatic carbon from quantitative analysis of the 3.4 μ m interstellar feature, providing that the absorption coefficient of interstellar aliphatic hydrocarbon is known. We produced interstellar dust analogues with spectra closely matching astronomical observations. Using a combination of FTIR and 13 C NMR spectroscopy, we determined an integrated absorption coefficient of the aliphatic component. The results thus obtained permit direct calibration of astronomical observations, providing rigorous estimates of the amount of aliphatic carbon in the ISM.
Hydrogen-atom attack on phenol and toluene is ortho-directed
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5CP07619F
Abstract: The reaction of H + phenol and H/D + toluene has been studied in a supersonic expansion after electric discharge.
Interplay between the hot phonon effect and intervalley scattering on the cooling rate of hot carriers in GaAs and InP
Publisher: Wiley
Date: 02-06-2011
DOI: 10.1002/PIP.1121
First-Principles Calculation of Triplet Exciton Diffusion in Crystalline Poly(p-phenylene vinylene)
Publisher: American Chemical Society (ACS)
Date: 14-10-2019
A new role of curcumin: as a multicolor photoinitiator for polymer fabrication under household UV to red LED bulbs
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5PY00661A
Abstract: Curcumin can act as a multicolor photoinitiator in free radical photopolymerization under air upon exposure to household LED bulbs.
A Marcus-Hush Perspective on Adiabatic Singlet Fission
Publisher: American Chemical Society (ACS)
Date: 25-04-2019
DOI: 10.26434/CHEMRXIV.8038892
Abstract: Singlet fission is a process whereby a bichromophoric system crosses from an excitonically coupled singlet state to a singlet-coupled triplet pair state. If the electronic structure is described locally, then the process may be described by a formal exchange of electrons. As such, it lends itself to a treatment rooted in the Marcus-Hush description of electron transfer. Here we use ab initio and density functional electronic structure theories to reveal a Marcus-Hush perspective on singlet fission and propose experiments to probe singlet fission in the spirit of photo-induced electron transfer. /
Double-resonance spectroscopy of radicals: Higher electronic excited states of 1- and 2-naphthylmethyl, 1-phenylpropargyl and 9-anthracenylmethyl
Publisher: Informa UK Limited
Date: 17-04-2015
Singlet and Triplet Exciton Dynamics of Violanthrone
Publisher: American Chemical Society (ACS)
Date: 30-03-2021
DOI: 10.26434/CHEMRXIV.14331737.V1
Abstract: The exciton dynamics of violanthrone-79 are investigated in solution and in the solidstate. In solution, the photo-prepared singlet is found to exhibit a strong ground-state bleachand stimulated emission feature, but when sensitized in its triplet state, exhibits only a narrowand weak ground-state bleach. As supported by density functional theory calculations,this is explained by the triplet state having absorptions in the same region, with a similaroscillator strength, as the ground state molecule. In solid films, the excited singlet isfound to survive only 100 ps, giving way to a long-lived transient absorption spectrum withcharacteristics reminiscent of the triplet in solution. This is interpreted in terms of singletfission in the solid film.
An All-Photonic Molecular Amplifier and Binary Flip-flop
Publisher: American Chemical Society (ACS)
Date: 25-11-2020
DOI: 10.26434/CHEMRXIV.13277855.V2
Abstract: A chemical system is proposed that is capable of lifying small optical inputs into large changes in internal composition, based on a feedback interaction between switchable fluorescence and visible-light photoswitching. This system would demonstrate bifurcating reaction kinetics under irradiation and reach one of two stable photostationary states depending on the initial composition of the system. This behavior would allow the system to act as a chemical realization of the flip-flop circuit, the fundamental element in sequential logic and binary memory storage. We use detailed numerical modeling to demonstrate the feasibility of the proposed behavior based on known molecular phenomena, and comment on some of the conditions required to realize this system.
An All-Photonic Molecular Amplifier and Binary Flip-flop
Publisher: American Chemical Society (ACS)
Date: 24-11-2020
DOI: 10.26434/CHEMRXIV.13277855.V1
Abstract: A chemical system is proposed that is capable of lifying small optical inputs into large changes in internal composition, based on a feedback interaction between switchable fluorescence and visible-light photoswitching. This system would demonstrate bifurcating reaction kinetics under irradiation and reach one of two stable photostationary states depending on the initial composition of the system. This behavior would allow the system to act as a chemical realization of the flip-flop circuit, the fundamental element in sequential logic and binary memory storage. We use detailed numerical modeling to demonstrate the feasibility of the proposed behavior based on known molecular phenomena, and comment on some of the conditions required to realize this system.
Jet-Cooled Spectroscopy of ortho-Hydroxycyclohexadienyl Radicals
Publisher: American Chemical Society (ACS)
Date: 12-10-2018
Abstract: The electronic spectra of the ortho-hydroxycyclohexadienyl radical have been observed following the supersonic expansion of the electric discharge products of phenol and water. Hydrogen atoms, split from water, add to the phenol ring at the ortho position, generating syn and anti rotamers with respect to the hydroxyl group. The D
Quantum-Induced Symmetry Breaking in the Deuterated Dihydroanthracenyl Radical
Publisher: American Chemical Society (ACS)
Date: 16-07-2019
Abstract: The hydrogen-atom adduct with anthracene, 9-dihydroanthracenyl radical (C
The eΠg3 state of C2: A pathway to dissociation
Publisher: AIP Publishing
Date: 14-07-2017
DOI: 10.1063/1.4985882
Abstract: The lowest 13 vibrational levels, v = 0–12, of the eΠg3 state of the C2 molecule have been measured by laser-induced fluorescence of new bands of the Fox-Herzberg system. The newly observed levels, v = 5–12, which span the eΠg3 electronic state up to and beyond the first dissociation threshold of C2, were analyzed to afford highly accurate molecular constants, including band origins, and rotational and spin-orbit constants. The spin-orbit coupling constants of the previously published lowest five levels are revised in sign and magnitude, requiring an overhaul of previously published molecular constants. The analysis is supported by high level ab initio calculations. Lifetimes of all observed levels were recorded and found to be in excellent agreement with ab initio predicted values up to v = 11. v = 12 was found to exhibit a much reduced lifetime and fluorescence quantum yield, which is attributed to the onset of predissociation. This brackets the dissociation energy of ground state XΣg+1 C2 between 6.1803 and 6.2553 eV, in agreement with the Active Thermochemical Tables.
Synthesis and Luminescence Properties of Iridium(III) Azide- and Triazole-Bisterpyridine Complexes
Publisher: MDPI AG
Date: 26-07-2013
Quantum-Induced Symmetry-Breaking in the Deuterated Dihydroanthracenyl Radical
Publisher: American Chemical Society (ACS)
Date: 15-05-2019
DOI: 10.26434/CHEMRXIV.8123648.V1
Abstract: The hydrogen-atom adduct with anthracene, 9-dihydroanthracenyl radical (C 14 H 11 ), and its deuterated analogue, have been identified by laser spectroscopy coupled to time-of-flight mass spectrometry, supported by time-dependent density functional theory calculations. The electronic spectrum of 9-dihydroanthracenyl radical exhibits an origin band at 19115 cm -1 and its ionization energy was determined to be 6.346(1) eV. The spectra reveal a low-frequency vibrational progression corresponding to a mode described by a butterfly-inversion. In the deuterated analogue, a zero-point-energy imbalance along this coordinate is found to lead to a doubling of the observed spectral lines in the progression. This is attributed to quantum-induced symmetry breaking as previously observed in isotopologues of CH 5 + .
Related Organisations
University Of Cambridge
Location: United Kingdom of Great Britain and Northern Ireland
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