ORCID Profile
0000-0003-1848-507X
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
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.
Physical Chemistry (Incl. Structural) | Structural Chemistry and Spectroscopy | Chemical Spectroscopy | Structural Chemistry | Physical Chemistry of Materials | Atomic and Molecular Physics | Nanotechnology | Colloid And Surface Chemistry | Quantum Chemistry | Physical Chemistry not elsewhere classified | Chemical Thermodynamics and Energetics | Nanochemistry and Supramolecular Chemistry | Characterisation Of Macromolecules | Quantum Chemistry | Mechanisms Of Reactions | Supramolecular Chemistry | Energy Generation, Conversion and Storage Engineering | Nanotechnology | Optics And Opto-Electronic Physics
Chemical sciences | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Physical sciences | Biological sciences | Hydrogen Production from Renewable Energy | Solar-Photovoltaic Energy |
Publisher: AIP Publishing
Date: 05-2012
DOI: 10.1063/1.4709496
Abstract: Measurement of the power spectral density of (stochastic) Brownian fluctuations of micro- and nano-devices is used frequently to gain insight into their mechanistic properties. Noise is always present in these measurements and can directly influence any parameter estimation obtained through a least-squares analysis. Importantly, measurements of the spectral density of stationary random signals, such as Brownian motion, inherently contain multiplicative noise. In this article, we theoretically analyze the impact of multiplicative noise on fit parameters extracted using a least-squares analysis. A general analysis is presented that is valid for any fit function with any number of fit parameters. This yields closed-form expressions for the expected value and variance in the fit parameters and provides a rigorous theoretical framework for a priori determination of the effect of measurement uncertainty. The theory is demonstrated and validated through Monte Carlo simulation of synthetic data and by comparison to power spectral density measurements of the Brownian fluctuations of an atomic force microscope cantilever – analytical formulas for the uncertainty in the fitted resonant frequency and quality factor are presented. The results of this study demonstrate that precise measurements of fit parameters in the presence of noise are inherently problematic – in idual measurements of the power spectral density are capable of yielding fit parameters that are many standard deviations away from the mean, with finite probability. This is of direct relevance to a host of applications in measurement science, including those connected with the atomic force microscope.
Publisher: American Chemical Society (ACS)
Date: 17-11-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP01240E
Abstract: The electrocyclisation and cycloreversion of charge-tagged dithienylethene molecules is explored in the gas phase using tandem ion mobility mass spectrometry.
Publisher: AIP Publishing
Date: 08-2002
DOI: 10.1063/1.1486435
Abstract: Midinfrared spectra of the Br−81-H2 and I−-H2 anion complexes are measured in the H-H stretch region by monitoring the production of halide anion photofragments. The spectra, which are assigned to complexes containing ortho H2, exhibit rotationally resolved ∑-∑ bands whose origins are redshifted from the molecular hydrogen Q1(1) transition by 110.8 cm−1 (Br−-H2) and 74.1 cm−1 (I−-H2). The complexes are deduced to possess linear equilibrium structures, with vibrationally averaged intermolecular separations between the halide anion and H2 center of mass of 3.461 Å (Br−-H2) and 3.851 Å (I−-H2). Vibrational excitation of the H2 subunit causes the intermolecular bond to stiffen and contract by 0.115 Å (Br−-H2) and 0.112 Å (I−-H2). Rydberg–Klein–Rees inversion of the spectroscopic data is used to generate effective radial potential energy curves near the potential minimum that are joined to long-range potential energy curves describing the interaction between an H2 molecule and a point negative charge. From these curves the dissociation energies of Br−-H2 and I−-H2 with respect to isolated H2 (j=1) and halide fragments are estimated as 365 and 253 cm−1, respectively.
Publisher: Elsevier BV
Date: 02-2003
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CP03244K
Abstract: Photo-induced proton transfer, deprotomer-dependent photochemistry, and intramolecular charge transfer in flavin anions are investigated using action spectroscopy.
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.
Publisher: Elsevier BV
Date: 05-2008
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP40828G
Abstract: The neurotransmitter analogue p-aminophenethylamine (APEA) illustrates many of the pitfalls and challenges associated with spectroscopic and conformational analysis of flexible molecules. The combined experimental-theoretical study presented here resolves a long-standing controversy over its conformational energetic preferences. Jet-cooled resonance enhanced two-photon ionisation (R2PI) and IR-UV ion depletion techniques enabled conformer-specific IR spectra in the NH-CH stretch region to be measured for four distinct conformers of APEA. Comparison of spectra with theoretical calculations (including MP2, M06-2X and B3LYP with aug-cc-pVTZ basis sets) allows the two most populated conformers to be unambiguously identified as those having a gauche arrangement of the side chain, which facilitates an NH···π type hydrogen bond. The other two observed conformers are assigned to structures with an anti-side chain. A fifth gauche conformer, predicted to be least stable, is not observed. Comparison with published conformer specific IR spectra of tyramine (Makara et al., J. Phys. Chem. A, 2008, 112, 13463-13469) and Raman spectra of phenylethylamine (Golan et al., J. Chem. Phys., 2009, 131, 024305) reveals an entirely consistent pattern of spectral signatures associated with the four specific conformations of the ethylamine side chain evident in APEA, and aids assignment of the associated CH and NH stretch fundamentals, some of which have very weak IR intensities. Extensive calculations of the relative energetic trends of the five conformers have been carried out. In comparison to the highest level of theory considered, CCSD(T)-F12b/cc-pVDZ-F12, MP2 overestimate the energy difference, whereas DFT significantly underestimates the energetic preference for NH···π stabilised gauche conformers, although inclusion of dispersion (M06-2X, B3LYP-D3) improves the DFT results.
Publisher: American Chemical Society (ACS)
Date: 04-09-2008
DOI: 10.1021/JA8018302
Abstract: Structural properties of the B(+)-H2 electrostatic complex are investigated through its rotationally resolved infrared spectrum in the H-H stretch region (3905-3975 cm(-1)). The spectrum, which was obtained by monitoring B(+) photofragments while the IR wavelength was scanned, is consistent with the complex having a T-shaped structure and a vibrationally averaged intermolecular separation of 2.26 A, which decreases by 0.04 A when the H2 subunit is vibrationally excited. The H-H stretch transition of B(+)-H2 is red-shifted by 220.6 +/- 1.5 cm(-1) from that of the free H2 molecule, much more than for other dihydrogen complexes with comparable binding energies. Properties of B(+)-H2 and the related Li(+)-H2, Na(+)-H2, and Al(+)-H2 complexes are explored through ab initio calculations at the MP2/aug-cc-pVTZ level. The unusually large red-shift for B(+)-H2 is explained as due to electron donation from the H2 sigma(g) bonding orbital to the unoccupied 2p(z) orbital on the B(+) ion.
Publisher: AIP Publishing
Date: 22-08-2017
DOI: 10.1063/1.4990572
Abstract: The B̃
Publisher: AIP Publishing
Date: 25-05-2007
DOI: 10.1063/1.2738464
Abstract: The Li+–(H2)n n=1–3 complexes are investigated through infrared spectra recorded in the H–H stretch region (3980–4120cm−1) and through ab initio calculations at the MP2∕aug-cc-pVQZ level. The rotationally resolved H–H stretch band of Li+–H2 is centered at 4053.4cm−1 [a −108cm−1 shift from the Q1(0) transition of H2]. The spectrum exhibits rotational substructure consistent with the complex possessing a T-shaped equilibrium geometry, with the Li+ ion attached to a slightly perturbed H2 molecule. Around 100 rovibrational transitions belonging to parallel Ka=0-0, 1-1, 2-2, and 3-3 subbands are observed. The Ka=0-0 and 1-1 transitions are fitted by a Watson A-reduced Hamiltonian yielding effective molecular parameters. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 2.056Å increasing by 0.004Å when the H2 subunit is vibrationally excited. The spectroscopic data are compared to results from rovibrational calculations using recent three dimensional Li+–H2 potential energy surfaces [Martinazzo et al., J. Chem. Phys. 119, 11241 (2003) Kraemer and Špirko, Chem. Phys. 330, 190 (2006)]. The H–H stretch band of Li+–(H2)2, which is centered at 4055.5cm−1 also exhibits resolved rovibrational structure. The spectroscopic data along with ab initio calculations support a H2–Li+–H2 geometry, in which the two H2 molecules are disposed on opposite sides of the central Li+ ion. The two equivalent Li+⋯H2 bonds have approximately the same length as the intermolecular bond in Li+–H2. The Li+–(H2)3 cluster is predicted to possess a trigonal structure in which a central Li+ ion is surrounded by three equivalent H2 molecules. Its infrared spectrum features a broad unresolved band centered at 4060cm−1.
Publisher: American Chemical Society (ACS)
Date: 02-03-2020
Publisher: American Chemical Society (ACS)
Date: 03-08-2017
Abstract: The utility of tandem ion mobility mass spectrometry coupled with electronic spectroscopy to investigate protomer-specific photochemistry is demonstrated by measuring the photoisomerization response for protomers of protonated 4-dicyanomethylene-2-methyl-6-para-dimethylaminostyryl-4H-pyran (DCM) molecules. The target DCMH
Publisher: Optica Publishing Group
Date: 15-07-2006
DOI: 10.1364/OL.31.002211
Abstract: Nondegenerate azimuthal morphology-dependent resonances are observed for a distorted, fluorescently labeled polystyrene microsphere levitated in a quadrupole ion trap. Modeling the in idual resonances by using perturbation theory allows a determination of quadrupole and octupole distortion parameters. The particle's shape changes slowly over the course of the measurement and eventually becomes spherical. The morphological changes are facilitated by laser heating of the particle above the polystyrene glass transition temperature. We demonstrate a method of transforming a trapped particle to a sphere and rendering its azimuthal modes degenerate.
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B508731G
Abstract: Infrared spectra of mass-selected Cl- -C2H4 and Br- -C2H4 complexes are recorded in the vicinity of the ethylene CH stretching vibrations (2700-3300 cm(-1) using vibrational predissociation spectroscopy. Spectra of both complexes exhibit 6 prominent peaks in the CH stretch region. Comparison with calculated frequencies reveal that the 4 higher frequency bands are associated with CH stretching modes of the C2H4 subunit, while the 2 weaker bands are assigned as overtone or combinations bands gaining intensity through interaction with the CH stretches. Ab initio calculations at the MP2/aug-cc-pVDZ level suggest that C2H4 preferentially forms a single linear H-bond with Cl- and Br- although a planar bifurcated configuration lies only slightly higher in energy (by 110 and 16 cm(-1), respectively). One-dimensional potential energy curves describing the in-plane intermolecular bending motion are developed which are used to determine the corresponding vibrational energies and wavefunctions. Experimental and theoretical results suggest that in their ground vibrational state the Cl- -C2H4 and Br- -C2H4 complexes are localized in the single H-bonded configuration, but that with the addition of modest amounts of internal energy, the in-plane bending wavefunction also has significant litude in the bifurcated structure.
Publisher: American Chemical Society (ACS)
Date: 30-04-2009
DOI: 10.1021/JP9031767
Abstract: We have recorded the rotationally resolved infrared spectrum of the weakly bound Mn+-H2 complex in the H-H stretch region (4022-4078 cm(-1)) by monitoring Mn+ photodissociation products. The band center of Mn+-H2, the H-H stretch transition, is shifted by -111.8 cm(-1) from the transition of the free H2 molecule. The spectroscopic data suggest that the Mn+-H2 complex consists of a slightly perturbed H2 molecule attached to the Mn+ ion in a T-shaped configuration with a vibrationally averaged intermolecular separation of 2.73 A. Together with the measured Mn+...H2 binding energy of 7.9 kJ/mol (Weis, P. et al. J. Phys. Chem. A 1997, 101, 2809.), the spectroscopic parameters establish Mn+-H2 as the most thoroughly characterized transition-metal cation-dihydrogen complex and a benchmark for calibrating quantum chemical calculations on noncovalent systems involving open d-shell configurations. Such systems are of possible importance for hydrogen storage applications.
Publisher: American Chemical Society (ACS)
Date: 29-09-2020
Publisher: AIP Publishing
Date: 15-07-2000
DOI: 10.1063/1.481919
Abstract: An infrared vibrational predissociation spectrum of the Br−79–C2H2 anion complex has been recorded over the 2800–3400 cm−1 range. Bands are observed that correspond to excitation of bound and free C–H stretches of an acetylene molecule engaged in a linear hydrogen bond with Br−. The band associated with the bound C–H stretch displays rotationally resolved substructure. Lower J transitions are absent from the predissociation spectrum, indicating that the upper levels lie below the dissociation threshold. Analysis leads to constants for lower and upper states: v0=2981.28, B″=0.048 84, ΔB=9.3×10−4 cm−1, and a minimum J′=28 for dissociation. The rotational constants correspond to vibrationally averaged separation between Br− and the C2H2 center of mass of 4.11 Å in the ground state and 4.07 Å in the v3 state. A dissociation energy for Br−–C2H2 of 3020±3 cm−1 is estimated from the energy of the lowest dissociating level. The spectroscopically derived data are corroborated by ab initio calculations conducted at the MP2/aug-cc-pVTZ level.
Publisher: American Chemical Society (ACS)
Date: 08-12-2016
DOI: 10.1021/ACS.ANALCHEM.6B04000
Abstract: An ion mobility spectrometer (IMS) with an electrospray ion source is used to investigate photo and thermal isomerization of photoactive molecules in the electrospray syringe. A light emitting diode adjacent to the syringe establishes a photostationary state that relaxes thermally toward the more stable isomer once illumination ceases. The arrangement is demonstrated by measuring Z-E thermal isomerization rates for several azoheteroarene compounds. The IMS technique has a distinct advantage over UV-vis spectrophotometry for measuring isomer populations in situations where there are multiple isomers with overlapping absorption profiles. In another development, an LED array adjacent to the silica capillary connecting the syringe to the electrospray ion source, is used to activate photochromic molecules, and investigate sequential photoswitching events.
Publisher: American Chemical Society (ACS)
Date: 31-07-2019
Abstract: Electronic spectra of mass-selected HC
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CP01733B
Abstract: Reversible E – Z photoswitching of a protonated azoheteroarene is demonstrated using ion mobility mass spectrometry.
Publisher: Elsevier BV
Date: 09-2006
Publisher: AIP Publishing
Date: 27-07-2006
DOI: 10.1063/1.2218334
Abstract: The infrared spectrum of mass selected Li+–D2 cations is recorded in the D–D stretch region (2860–2950cm−1) in a tandem mass spectrometer by monitoring Li+ photofragments. The D–D stretch vibration of Li+–D2 is shifted by −79cm−1 from that of the free D2 molecule indicating that the vibrational excitation of the D2 subunit strengthens the effective Li+⋯D2 intermolecular interaction. Around 100 rovibrational transitions, belonging to parallel Ka=0-0, 1-1, and 2-2 subbands, are fitted to a Watson A-reduced Hamiltonian to yield effective molecular parameters. The infrared spectrum shows that the complex consists of a Li+ ion attached to a slightly perturbed D2 molecule with a T-shaped equilibrium configuration and a 2.035Å vibrationally averaged intermolecular separation. Comparisons are made between the spectroscopic data and data obtained from rovibrational calculations using a recent three dimensional Li+–D2 potential energy surface [R. Martinazzo, G. Tantardini, E. Bodo, and F. Gianturco, J. Chem. Phys. 119, 11241 (2003)].
Publisher: AIP Publishing
Date: 12-11-2008
DOI: 10.1063/1.3005785
Abstract: The rotationally resolved infrared spectrum of the Na+–H2 cation complex is recorded in the H–H stretch region (4067–4118 cm−1) by monitoring the production of Na+ photofragments. Altogether 42 lines are identified, 40 of which are assigned to Ka=1-1 transitions (associated with complexes containing ortho-H2) and two tentatively assigned to Ka=0-0 transitions (associated with complexes containing para-H2). The Ka=1-1 subband lines were fitted using a Watson A-reduced Hamiltonian, yielding effective spectroscopic constants. The band origin is estimated as 4094.6 cm−1, a shift of −66.6 cm−1 with respect to the Q1(0) transition of the free H2 molecule. The results demonstrate that Na+–H2 has a T-shaped equilibrium configuration with the Na+ ion attached to a slightly perturbed H2 molecule but that large- litude vibrational motions significantly influence the rotational constants derived from the asymmetric rigid rotor analysis. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 2.493 Å, increasing slightly (by 0.002 Å) when the H2 subunit is vibrationally excited. A new three-dimensional potential energy surface is developed to describe the Na+–H2 complex. Ab initio points calculated using the CCSD(T) method and aug-cc-pVQZ basis set augmented by bond functions are fitted using a reproducing kernel Hilbert space method [Ho et al., J. Chem. Phys. 104, 2584 (1996)] to give an analytical representation of the potential energy surface. Ensuing variational calculations of the rovibrational energy levels demonstrate that the potential energy surface correctly predicts the frequency of the νHH transition (to within 2.9 cm−1) and the dissociation energies [842 cm−1 for Na+–H2(para) and 888 cm−1 for Na+–H2(ortho)]. The B and C rotational constants are slightly underestimated (by 1.7%), while the vibrationally averaged intermolecular separation is overestimated by 0.02 Å.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR08321A
Abstract: The structure of a large dicationic silver hydride nanocluster was determined by X-ray crystallography. Pathways to the gas-phase liberation of hydrogen have been identified.
Publisher: American Chemical Society (ACS)
Date: 23-09-2022
Publisher: American Chemical Society (ACS)
Date: 15-09-2022
Abstract: Electronic spectra are measured for protonated carbon clusters (C
Publisher: AIP Publishing
Date: 25-01-2017
DOI: 10.1063/1.4974338
Abstract: The electronic spectrum of the methyl propargyl cation (2-butyn-1-yl cation, H
Publisher: Elsevier BV
Date: 05-2007
Publisher: American Chemical Society (ACS)
Date: 15-06-2020
Publisher: American Chemical Society (ACS)
Date: 23-09-2020
Publisher: AIP Publishing
Date: 10-2012
DOI: 10.1063/1.4757398
Abstract: The spring constant of an atomic force microscope cantilever is often needed for quantitative measurements. The calibration method of Sader et al. [Rev. Sci. Instrum. 70, 3967 (1999)]10.1063/1.1150021 for a rectangular cantilever requires measurement of the resonant frequency and quality factor in fluid (typically air), and knowledge of its plan view dimensions. This intrinsically uses the hydrodynamic function for a cantilever of rectangular plan view geometry. Here, we present hydrodynamic functions for a series of irregular and non-rectangular atomic force microscope cantilevers that are commonly used in practice. Cantilever geometries of arrow shape, small aspect ratio rectangular, quasi-rectangular, irregular rectangular, non-ideal trapezoidal cross sections, and V-shape are all studied. This enables the spring constants of all these cantilevers to be accurately and routinely determined through measurement of their resonant frequency and quality factor in fluid (such as air). An approximate formulation of the hydrodynamic function for microcantilevers of arbitrary geometry is also proposed. Implementation of the method and its performance in the presence of uncertainties and non-idealities is discussed, together with conversion factors for the static and dynamic spring constants of these cantilevers. These results are expected to be of particular value to the design and application of micro- and nanomechanical systems in general.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CP01624D
Abstract: The photoinduced excited state dynamics of gas-phase trans-retinoate (deprotonated trans-retinoic acid, trans-RA
Publisher: AIP Publishing
Date: 13-07-2023
DOI: 10.1063/5.0152570
Abstract: Electronic transitions are observed for the O2+–Ar and O2+–N2 complexes over the 225–350 nm range. The transitions are not associated with recognized electronic band systems of the respective atomic and diatomic constituents (Ar+, Ar, O2+, O2, N2+, and N2) but rather are due to charge transfer transitions. Onsets of the O2+–Ar and O2+–N2 band systems occur at 3.68 and 3.62 eV, respectively, corresponding to the difference in the ionization potentials of Ar and O2 (3.69 eV), and N2 and of O2 (3.51 eV), suggesting the band systems arise from intramolecular charge transfer transitions to states correlating with O2(X3Σg−) + Ar+ (2Pu) and O2(X3Σg−) + N2+(X2Σg+) limits, respectively. The dominant vibronic progressions have ωe values of 1565 cm−1 for O2+–Ar and 1532 cm−1 for O2+–N2, reasonably close to the value for the neutral O2 molecule in its X3Σg− state (1580 cm−1). Higher energy band systems for O2+–Ar and O2+–N2 are assigned to transitions to states correlating with the O2 (a1Δg) + Ar+ (2Pu) and O2 (a1Δg) + N2+(X2Σg+) limits, respectively.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CP02818K
Abstract: PMMA polymer films doped with photochromic molecules have been prepared that can be photoswitched between three states and display novel fluorescence behavior.
Publisher: American Chemical Society (ACS)
Date: 24-01-2018
DOI: 10.1021/ACS.JPCLETT.7B03402
Abstract: Donor-acceptor Stenhouse adducts (DASAs) are a new class of photoswitching molecules with excellent fatigue resistance and synthetic tunability. Here, tandem ion mobility mass spectrometry coupled with laser excitation is used to characterize the photocyclization reaction of isolated, charge-tagged DASA molecules over the 450-580 nm range. The experimental maximum response at 530 nm agrees with multireference perturbation theory calculations for the S
Publisher: American Chemical Society (ACS)
Date: 05-09-2013
DOI: 10.1021/JP405747Q
Abstract: Molecular photoisomerization plays a crucial role in erse biological and technological contexts. Here, we combine ion mobility spectrometry and laser spectroscopy to characterize the photoisomerization of molecular cations in the gas phase. The target molecular ions, polymethine dye cations 3,3'-diethylthiacarbocyanine (DTC(+)), are propelled through helium buffer gas by an electric field and are photoisomerized by light from a tunable laser. Photoexcitation over the 450-570 nm range converts trans-DTC(+) to cis-DTC(+), noticeably modifying the ions' arrival time distribution. The photoisomerization action spectrum, which has a maximum at 535 nm, resembles the absorption spectrum of DTC(+) in solution but is shifted 25 nm to shorter wavelength. Comparisons between measured and calculated mobilities suggest that the photoisomer involves a twist about the second C-C bond in the methine chain (8,9-cis isomer) rather than a twist about the first methine C-C bond (2,8-cis isomer). It is postulated that the excited gas-phase ions internally convert from the S1 Franck-Condon region to the S0 manifold and explore the conformational landscape as they cool through He buffer gas collisions. Master equation simulations of the relaxation process in the S0 manifold suggest that the 8,9-cis isomer is preferred over the 2,8-cis isomer because it lies lower in energy and because it is separated from the trans isomer by a substantially higher barrier. The study demonstrates that the photoisomerization of molecular ions can be probed selectively in the gas phase, providing insights into photoisomerization mechanisms and information on the solvent-free absorption spectrum.
Publisher: American Chemical Society (ACS)
Date: 03-05-2018
DOI: 10.1021/ACS.JPCLETT.8B01201
Abstract: Fluorescent proteins have revolutionized the visualization of biological processes, prompting efforts to understand and control their intrinsic photophysics. Here we investigate the photoisomerization of deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/CH04149
Abstract: Ab initio calculations are performed at the MP2/aug-cc-pVTZ level for F−-CH4 and Cl−-CH4, to show that the dimers have C3v symmetry with the CH4 sub-unit attached to the halide anion by a single hydrogen bond. This geometry is consistent with infrared spectra of F−-CH4 and Cl−-CH4 recorded in the CH-stretch region. The calculations also indicate substantial anharmonicity in the H-bonded CH stretch of F−-CH4. Infrared spectra of the F−-(CH4)2 and Cl−-(CH4)2 trimer clusters are consistent with structures that have two equivalent CH4 sub-units H-bonded to the halide core. Additional bands in the F−-(CH4)2 spectrum are assigned as transitions to CH4 bending overtone and combination levels, gaining infrared intensity from Fermi interaction with the H-bonded CH stretch.
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.
Publisher: AIP Publishing
Date: 24-10-2003
DOI: 10.1063/1.1615519
Abstract: Vibrational predissociation spectroscopy is used to obtain infrared spectra of the Cl−–C6H6, Br−–C6H6, and I−–C6H6 complexes in the region of the benzene CH stretch vibrations (2800–3200 cm−1). The infrared spectra of the three dimers are similar, each exhibiting several narrow bands (full width at half maximum & cm−1) that are only slightly redshifted from the absorptions of the free benzene molecule. Ab initio calculations predict that the most stable form of the three complexes is a planar C2v structure in which the halide is hydrogen bonded to two adjacent CH groups. The planar C2v structure in which the halide is linearly H bonded to a single CH group is predicted to be slightly less stable than the bifurcated form. Comparisons between experimental and theoretically predicted infrared spectra confirm that the bifurcated structure is indeed the most stable conformer for all three complexes. Ab initio calculations show that the electron density transfer from the halide to the benzene is not limited to the σ*(CH) orbitals adjacent to the halide, but extends to the σ domain of the benzene ring, consistent with the moderate shift of the CH stretch frequencies. The presence of weak satellite bands is explained in terms of Fermi resonances reminiscent of the benzene Fermi tetrad or hot bands involving the in-plane intermolecular bend vibration.
Publisher: AIP Publishing
Date: 25-10-2007
DOI: 10.1063/1.2778422
Abstract: The infrared spectrum of the Al+–H2 complex is recorded in the H–H stretch region (4075–4110cm−1) by monitoring Al+ photofragments. The H–H stretch band is centered at 4095.2cm−1, a shift of −66.0cm−1 from the Q1(0) transition of the free H2 molecule. Altogether, 47 rovibrational transitions belonging to the parallel Ka=0-0 and 1-1 subbands were identified and fitted using a Watson A-reduced Hamiltonian, yielding effective spectroscopic constants. The results suggest that Al+–H2 has a T-shaped equilibrium configuration with the Al+ ion attached to a slightly perturbed H2 molecule, but that large- litude intermolecular vibrational motions significantly influence the rotational constants derived from an asymmetric rotor analysis. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 3.03Å, decreasing by 0.03Å when the H2 subunit is vibrationally excited. A three-dimensional potential energy surface for Al+–H2 is calculated ab initio using the coupled cluster CCSD(T) method and employed for variational calculations of the rovibrational energy levels and wave functions. Effective dissociation energies for Al+–H2(para) and Al+–H2(ortho) are predicted, respectively, to be 469.4 and 506.4cm−1, in good agreement with previous measurements. The calculations reproduce the experimental H–H stretch frequency to within 3.75cm−1, and the calculated B and C rotational constants to within ∼2%. Agreement between experiment and theory supports both the accuracy of the ab initio potential energy surface and the interpretation of the measured spectrum.
Publisher: American Chemical Society (ACS)
Date: 27-01-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7CP07278C
Abstract: Substituted azobenzenes serve as chromophores and actuators in a wide range of molecular photoswitches.
Publisher: American Chemical Society (ACS)
Date: 02-06-2017
Abstract: Collision-induced dissociation mass spectrometry of the ammonium ions 4a and 4b results in the formation of the seleniranium ion 5, the structure and purity of which were verified using gas-phase infrared spectroscopy coupled to mass spectrometry and gas-phase ion-mobility measurements. Ion-molecule reactions between the ion 5 (m/z = 261) and cyclopentene, cyclohexene, cycloheptene, and cyclooctene resulted in the formation of the seleniranium ions 7 (m/z = 225), 6 (m/z = 239), 8 (m/z = 253), and 9 (m/z = 267), respectively. Further reaction of seleniranium 6 with cyclopentene resulted in further π-ligand exchange giving seleniranium ion 7, confirming that direct π-ligand exchange between seleniranium ion 5 and cycloalkenes occurs in the gas phase. Pseudo-first-order kinetics established relative reaction efficiencies for π-ligand exchange for cyclopentene, cyclohexene, cycloheptene. and cyclooctene as 0.20, 0.07, 0.43, and 4.32. respectively. DFT calculations at the M06/6-31+G(d) level of theory provide the following insights into the mechanism of the π-ligand exchange reactions the cycloalkene forms a complex with the seleniranium ion 5 with binding energies of 57 and 62 kJ/mol for cyclopentene and cyclohexene, respectively, with transition states for π-ligand exchange having barriers of 17.8 and 19.3 kJ/mol for cyclopentene and cyclohexene, respectively.
Publisher: Elsevier BV
Date: 10-2002
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/CH11032
Abstract: Infrared spectra and ab initio calculations are presented for gas phase clusters consisting of a fluoride anion attached to acetylene ligands. Spectra obtained in the C-H stretch region contain a single strong band, consistent with cluster structures in which roughly equivalent acetylene ligands are hydrogen bonded to a central fluoride anion core. Minimum energy structures predicted from ab initio calculations at the MP2 level of theory are highly symmetric with acetylene ligands equally spaced about a central fluoride anion core. The predicted H-bonded C-H stretching frequencies, after scaling to correct for anharmonicity, agree well with the experimental band positions.
Publisher: American Chemical Society (ACS)
Date: 18-08-2017
Abstract: Because of their high photoisomerization efficiencies, azobenzenes and their functionalized derivatives are used in a broad range of molecular photoswitches. Here, the photochemical properties of the trans isomers of protonated azobenzene (ABH
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP53454E
Abstract: The photophysical behaviour of a triphenylamine-based organic dye sensitizer (Carbz-PAHTDTT) attached to alumina and titania nanoparticles (labelled Carbz-Al and Carbz-Ti, respectively) is examined in the absence and presence of the chenodeoxycholic acid (CDCA) coadsorber. The experiments are conducted in vacuo by suspending the target dye-sensitized nanoparticles within a quadrupole ion trap, where they are probed with laser radiation to obtain emission spectra and time-resolved excited state decay curves. For Carbz-Al, the dye's emission band is blue-shifted and the excited state lifetime is increased upon the coabsorption of CDCA, effects attributed to reduced dye aggregation. Compared to Carbz-Al, the Carbz-Ti excited state lifetimes are significantly shorter due to excited dye molecules injecting electrons into the titania conduction band. For Carbz-Ti, the electron injection quantum yields for the surfaces with CDCA (CDCA : dye = 25 : 1) and without CDCA are estimated to be 0.87 and 0.71, respectively. The gas-phase results demonstrate that Carbz-PAHTDTT dye aggregates are detrimental to the performance of a dye-sensitized solar cell.
Publisher: AIP Publishing
Date: 09-2011
DOI: 10.1063/1.3632122
Abstract: The thermal noise spectrum of nanomechanical devices is commonly used to characterize their mechanical properties and energy dissipation. This spectrum is measured from finite time series of Brownian motion of the device, which is windowed and Fourier transformed. Here, we present a theoretical and experimental investigation of the effect of such finite s ling on the measured device quality factor. We prove that if no spectral window is used, the thermal noise spectrum retains its original Lorentzian distribution but with a reduced quality factor, indicating an apparent enhancement in energy dissipation. A simple analytical formula is derived connecting the true and measured quality factors – this enables extraction of the true device quality factor from measured data. Common windows used to reduce spectral leakage are found to distort the (true) Lorentzian shape, potentially making fitting problematic. These findings are expected to be of particular importance for devices with high quality factors, where spectral resolution can be limited in practice. Comparison and validation using measurements on atomic force microscope cantilevers are presented.
Publisher: AIP Publishing
Date: 04-2022
DOI: 10.1063/5.0085680
Abstract: Infrared and electronic spectra are indispensable for understanding the structural and energetic properties of charged molecules and clusters in the gas phase. However, the presence of isomers can potentially complicate the interpretation of spectra, even if the target molecules or clusters are mass-selected beforehand. Here, we describe an instrument for spectroscopically characterizing charged molecular clusters that have been selected according to both their isomeric form and their mass-to-charge ratio. Cluster ions generated by laser ablation of a solid s le are selected according to their collision cross sections with helium buffer gas using a drift tube ion mobility spectrometer and their mass-to-charge ratio using a quadrupole mass filter. The mobility- and mass-selected target ions are introduced into a cryogenically cooled, three-dimensional quadrupole ion trap where they are thermalized through inelastic collisions with an inert buffer gas (He or He/N2 mixture). Spectra of the molecular ions are obtained by tagging them with inert atoms or molecules (Ne and N2), which are dislodged following resonant excitation of an electronic transition, or by photodissociating the cluster itself following absorption of one or more photons. An electronic spectrum is generated by monitoring the charged photofragment yield as a function of wavelength. The capacity of the instrument is illustrated with the resonance-enhanced photodissociation action spectra of carbon clusters (Cn+) and polyacetylene cations (HC2nH+) that have been selected according to the mass-to-charge ratio and collision cross section with He buffer gas and of mass-selected Au2+ and Au2Ag+ clusters.
Publisher: AIP Publishing
Date: 02-12-2021
DOI: 10.1063/5.0070502
Abstract: Electronic spectra are measured for mass-selected C
Publisher: American Chemical Society (ACS)
Date: 06-12-2021
DOI: 10.1021/ACS.JPCLETT.1C03532
Abstract: Internal conversion between valence-localized and dipole-bound states is thought to be a ubiquitous process in polar molecular anions, yet there is limited direct evidence. Here, photodetachment action spectroscopy and time-resolved photoelectron imaging with a heteropolycyclic aromatic hydrocarbon (hetero-PAH) anion, deprotonated 1-pyrenol, is used to demonstrate a subpicosecond (τ
Publisher: American Chemical Society (ACS)
Date: 08-12-2021
DOI: 10.1021/ACS.JPCLETT.1C03456
Abstract: Iodinate anions are important in the chemistry of the atmosphere where they are implicated in ozone depletion and particle formation. The atmospheric chemistry of iodine is a complex overlay of neutral-neutral, ion-neutral, and photochemical processes, where many of the reactions and intermediates remain poorly characterized. This study targets the visible spectroscopy and photostability of the gas-phase hypoiodite anion (IO
Publisher: American Chemical Society (ACS)
Date: 02-04-2018
DOI: 10.1021/ACS.ANALCHEM.8B00469
Abstract: Separation and structural identification of lipids remain a major challenge for contemporary lipidomics. Regioisomeric lipids differing only in position(s) of unsaturation are often not differentiated by conventional liquid chromatography-mass spectrometry approaches leading to the incomplete, or sometimes incorrect, assignation of molecular structure. Here we describe an investigation of the gas phase separations by differential-mobility spectrometry (DMS) of a series of synthetic analogues of the recently described 1-deoxysphingosine. The dependence of the DMS behavior on the position of the carbon-carbon double bond within the ionized lipid is systematically explored and compared to trends from complementary investigations, including collision cross-sections measured by drift tube ion mobility, reaction efficiency with ozone, and molecular dynamics simulations. Consistent trends across these modes of interrogation point to the importance of direct, through-space interactions between the charge site and the carbon-carbon double bond. Differences in the geometry and energetics of this intramolecular interaction underpin DMS separations and influence reactivity trends between regioisomers. Importantly, the disruption and reformation of these intramolecular solvation interactions during DMS are proposed to be the causative factor in the observed separations of ionized lipids which are shown to have otherwise identical collision cross-sections. These findings provide key insights into the strengths and limitations of current ion-mobility technologies for lipid isomer separations and can thus guide a more systematic approach to improved analytical separations in lipidomics.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CP90049H
Publisher: AIP Publishing
Date: 28-09-2012
DOI: 10.1063/1.4754131
Abstract: The rotationally resolved infrared spectrum of the B+-D2 ion-neutral complex is recorded in the D-D stretch vibration region (2805–2875 cm−1) by detecting B+ photofragments. Analysis of the spectrum confirms a T-shaped equilibrium geometry for the B+-D2 complex with a vibrationally averaged intermolecular bond length of 2.247 Å, around 0.02 Å shorter than for the previously characterised B+-H2 complex [V. Dryza, B. L. J. Poad, and E. J. Bieske, J. Am. Chem. Soc. 130, 12986 (2008)10.1021/ja8018302]. The D-D stretch band centre occurs at 2839.76 ± 0.10 cm−1, representing a −153.8 cm−1 shift from the Q1(0) transition of the free D2 molecule. A new three dimensional ab initio potential energy surface for the B++H2 interaction is calculated using the coupled cluster RCCSD(T) method and is used in variational calculations for the rovibrational energies of B+-H2 and B+-D2. The calculations predict dissociation energies of 1254 cm−1 for B+-H2 with respect to the B++H2 (j = 0) limit, and 1313 cm−1 for B+-D2 with respect to the B++D2 (j = 0) limit. The theoretical approach reproduces the rotational and centrifugal constants of the B+-H2 and B+-D2 complexes to within 3%, and the magnitude of the contraction of the intermolecular bond accompanying excitation of the H2 or D2 sub-unit, but underestimates the H-H and D-D vibrational band shifts by 7%–8%. Combining the theoretical and experimental results allows a new, more accurate estimation for the B+-H2 band origin (3939.64 ± 0.10 cm−1).
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7AN00398F
Abstract: A new method for probing the photoisomerisation of molecules in solution using ion mobility mass spectrometry is described and demonstrated with a azoheteroarene photoswitch.
Publisher: American Chemical Society (ACS)
Date: 27-05-2007
DOI: 10.1021/JP070453R
Abstract: The Cl- -C6H5CH3*Ar, Cl- -C6H5NH2*Ar, and Cl- -C6H5OH*Ar anion complexes are investigated using infrared photodissociation spectroscopy and ab initio calculations at the MP2/aug-cc-pVDZ level. The results indicate that for Cl- -C6H5NH2 and Cl- -C6H5OH, the Cl- anion is attached to the substituent group by a single near-linear hydrogen bond. For Cl--C6H5CH3, the Cl- is attached to an ortho-hydrogen atom on the aromatic ring and to a hydrogen atom on the methyl group by a weaker hydrogen bond. The principal spectroscopic consequence of the hydrogen-bonding interaction in the three complexes is a red-shift and intensity increase for the CH, NH, and OH stretching modes. Complexities in the infrared spectra in the region of the hydrogen-bonded XH stretch band are associated with Fermi resonances between the hydrogen-stretching vibrational modes and bending overtone and combination levels. There are notable correlations between the vibrational red-shift, the elongation of the H-bonded XH group, and the proton affinity of the aromatic molecule's conjugate base.
Publisher: AIP Publishing
Date: 14-07-2004
DOI: 10.1063/1.1763569
Abstract: The rotationally resolved infrared photodissociation spectrum of Cl−-HD is measured in the HD stretch region. Two Σ-Σ bands are observed, corresponding to transitions from the ground state [the (vHD=0, n=0) level] and first excited intermolecular bend state [the (vHD=0, n=1) level]. The (vHD=0, n=0) and (vHD=0, n=1) states are predominantly associated with the linear Cl−⋯DH and Cl−⋯HD geometries, respectively. The spectrum is complicated by perturbative interactions between levels of the (vHD=0, n=0) and (vHD=0, n=1) rotational manifolds and between levels of the (vHD=1, n=0) and (vHD=1, n=1) rotational manifolds. A global fit to the transition frequencies, taking the lower and upper state perturbations into account, yields zero-order rotational and centrifugal distortion constants and allows us to establish that the (vHD=0, n=1, J″=0) level lies 13.7 cm−1 above the (vHD=0, n=0, J″=0) level. Rovibrational energy level calculations performed using a recent ab initio potential energy surface confirm the picture emerging from the experimental data and provide good agreement with measured molecular parameters. The results emphasize the importance of quantum mechanical interconversion between two isomeric structures of a simple anion complex.
Publisher: American Chemical Society (ACS)
Date: 17-04-2018
DOI: 10.1021/ACS.INORGCHEM.8B00871
Abstract: Ruthenium sulfoxide complexes undergo thermally reversible linkage isomerization of sulfoxide ligands from S- to O-bound in response to light. Here, we report photoisomerization action spectra for a ruthenium bis-sulfoxide molecular photoswitch, [Ru(bpy)
Publisher: Elsevier BV
Date: 05-2009
Publisher: American Chemical Society (ACS)
Date: 09-2005
DOI: 10.1021/JP053958V
Abstract: In an effort to elucidate their structures, mass-selected Cl--(CH4)n (n = 1-10) clusters are probed using infrared spectroscopy in the CH stretch region (2800-3100 cm(-1)). Accompanying ab initio calculations at the MP2/6-311++G(2df,2p) level for the n = 1-3 clusters suggest that methane molecules prefer to attach to the chloride anion by single linear H-bonds and sit adjacent to one another. These conclusions are supported by the agreement between experimental and calculated vibrational band frequencies and intensities. Infrared spectra in the CH stretch region for Cl--(CH4)n clusters containing up to ten CH4 ligands are remarkably simple, each being dominated by a single narrow peak associated with stretching motion of hydrogen-bonded CH groups. The observations are consistent with cluster structures in which at least ten equivalent methane molecules can be accommodated in the first solvation shell about a chloride anion.
Publisher: AIP Publishing
Date: 05-01-2015
DOI: 10.1063/1.4904267
Abstract: The S1←S0 electronic transition of the N-pyridinium ion (C5H5NH+) is investigated using ultraviolet photodissociation (PD) spectroscopy of the bare ion and also the N2-tagged complex. Gas-phase N-pyridinium ions photodissociate by the loss of molecular hydrogen (H2) in the photon energy range 37 000–45 000 cm−1 with structurally diagnostic ion-molecule reactions identifying the 2-pyridinylium ion as the exclusive co-product. The photodissociation action spectra reveal vibronic details that, with the aid of electronic structure calculations, support the proposal that dissociation occurs through an intramolecular rearrangement on the ground electronic state following internal conversion. Quantum chemical calculations are used to analyze the measured spectra. Most of the vibronic features are attributed to progressions of totally symmetric ring deformation modes and out-of-plane modes active in the isomerization of the planar excited state towards the non-planar excited state global minimum.
Publisher: American Chemical Society (ACS)
Date: 19-01-2002
DOI: 10.1021/JP0129075
Publisher: SAGE Publications
Date: 02-2010
DOI: 10.1255/EJMS.1049
Abstract: We describe recent experiments in which mass spectrometry and laser spectroscopy are combined to characterize Li + –H 2 , Na + –H 2 , B + –H 2 and Al + –H 2 complexes in the gas-phase. The infrared spectra, which feature full resolution of rotational sub-structures, are recorded by monitoring M + photofragments as the infrared wavelength is scanned. The spectra deliver detailed information on the way, in which a hydrogen molecule is attached to a metal cation including the intermolecular separation, the force constant for the intermolecular bond and the H–H stretching frequency. The complexes all possess T-shaped equilibrium geometries and display a clear correlation between the length and force constant of the intermolecular bond and the dissociation energy. In contrast, the data do not support any straight forward correlation between the frequency shift for the H–H stretch mode and the dissociation energy.
Publisher: Wiley
Date: 21-01-2020
Publisher: American Chemical Society (ACS)
Date: 04-01-2019
Abstract: The unimolecular reactions of C
Publisher: American Chemical Society (ACS)
Date: 10-12-2009
DOI: 10.1021/JP808807R
Abstract: Rotationally resolved infrared spectra of Mg(+)-H(2) and Mg(+)-D(2) are recorded in the H-H (4025-4080 cm(-1)) and D-D (2895-2945 cm(-1)) stretch regions by monitoring Mg(+) photofragments. The nu(HH) and nu(DD) transitions of Mg(+)-H(2) and Mg(+)-D(2) are red-shifted by 106.2 +/- 1.5 and 76.0 +/- 0.1 cm(-1) respectively from the fundamental vibrational transitions of the free H(2) and D(2) molecules. The spectra are consistent with a T-shaped equilibrium structure in which the Mg(+) ion interacts with a slightly perturbed H(2) or D(2) molecule. From the spectroscopic constants, a vibrationally averaged intermolecular separation of 2.716 A (2.687 A) is deduced for the ground state of Mg(+)-H(2) (Mg(+)-D(2)), decreasing by 0.037 A (0.026 A) when the H(2) (D(2)) subunit is vibrationally excited.
Publisher: American Chemical Society (ACS)
Date: 09-04-2019
Publisher: American Chemical Society (ACS)
Date: 12-2006
DOI: 10.1021/JP0654112
Abstract: Infrared spectra of mass-selected F- -(CH4)n (n = 1-8) clusters are recorded in the CH stretching region (2500-3100 cm-1). Spectra for the n = 1-3 clusters are interpreted with the aid of ab initio calculations at the MP2/6-311++G(2df 2p) level, which suggest that the CH4 ligands bind to F- by equivalent, linear hydrogen bonds. Anharmonic frequencies for CH4 and F--CH4 are determined using the vibrational self-consistent field method with second-order perturbation theory correction. The n = 1 complex is predicted to have a C3v structure with a single CH group hydrogen bonded to F-. Its spectrum exhibits a parallel band associated with a stretching vibration of the hydrogen-bonded CH group that is red-shifted by 380 cm-1 from the nu1 band of free CH4 and a perpendicular band associated with the asymmetric stretching motion of the nonbonded CH groups, slightly red-shifted from the nu3 band of free CH4. As n increases, additional vibrational bands appear as a result of Fermi resonances between the hydrogen-bonded CH stretching vibrational mode and the 2nu4 overtone and nu2+nu4 combination levels of the methane solvent molecules. For clusters with n < or = 8, it appears that the CH4 molecules are accommodated in the first solvation shell, each being attached to the F- anion by equivalent hydrogen bonds.
Publisher: AIP Publishing
Date: 02-06-2011
DOI: 10.1063/1.3596720
Abstract: The infrared spectrum of mass-selected Na+-D2 complexes is recorded in the D-D stretch vibration region (2915-2972 cm−1) by detecting Na+ photofragments resulting from photo-excitation of the complexes. Analysis of the rotationally resolved spectrum confirms a T-shaped equilibrium geometry for the complex and a vibrationally averaged intermolecular bond length of 2.461 Å. The D-D stretch band centre occurs at 2944.04 cm−1, representing a −49.6 cm−1 shift from the Q1(0) transition of the free D2 molecule. Variational rovibrational energy level calculations are performed for Na+-D2 utilising an ab initio potential energy surface developed previously for investigating the Na+-H2 complex [B. L. J. Poad et al., J. Chem. Phys. 129, 184306 (2008)]10.1063/1.3005785. The theoretical approach predicts a dissociation energy for Na+-D2 of 923 cm−1 with respect to the Na++ D2 limit, reproduces the experimental rotational constants to within 1-2%, and gives a simulated spectrum closely matching the experimental infrared spectrum.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8FD00217G
Abstract: Substituted naphthalene anions (deprotonated 2-naphthol and 6-hydroxy-2-naphthoic acid) are spectroscopically probed in a tandem drift tube ion mobility spectrometer (IMS). Target anions are selected according to their drift speed through nitrogen buffer gas in the first IMS stage before being exposed to a pulse of tunable light that induces either photodissociation or electron photodetachment, which is conveniently monitored by scavenging the detached electrons with trace SF6 in the buffer gas. The photodetachment action spectrum of the 2-naphtholate anion exhibits a band system spanning 380-460 nm with a prominent series of peaks spaced by 440 cm-1, commencing at 458.5 nm, and a set of weaker peaks near the electron detachment threshold corresponding to transitions to dipole-bound states. The two deprotomers of 6-hydroxy-2-naphthoic acid are separated and spectroscopically probed independently. The molecular anion formed from deprotonation of the hydroxy group gives rise to a photodetachment action spectrum similar to that of the 2-naphtholate anion with an onset at 470 nm and a maximum at 420 nm. Near the threshold, the photoreaction with SF6 is observed with displacement of an OH group by an F atom. In contrast, the anion formed from deprotonation of the carboxylic acid group gives rise to a photodissociation action spectrum, recorded on the CO2 loss channel, lying at much shorter wavelengths with an onset at 360 nm and maximum photoresponse at 325 nm.
Publisher: Elsevier BV
Date: 08-2004
Publisher: AIP Publishing
Date: 10-07-2023
DOI: 10.1063/5.0155548
Abstract: Understanding and controlling the chemical behavior of iron and iron oxide clusters requires accurate thermochemical data, which, because of the complex electronic structure of transition metal clusters, can be difficult to calculate reliably. Here, dissociation energies for Fe2+, Fe2O+, and Fe2O2+ are measured using resonance enhanced photodissociation of clusters contained in a cryogenically cooled ion trap. The photodissociation action spectrum of each species exhibits an abrupt onset for the production of Fe+ photofragments from which bond dissociation energies are deduced for Fe2+ (2.529 ± 0.006 eV), Fe2O+ (3.503 ± 0.006 eV), and Fe2O2+ (4.104 ± 0.006 eV). Using previously measured ionization potentials and electron affinities for Fe and Fe2, bond dissociation energies are determined for Fe2 (0.93 ± 0.01 eV) and Fe2− (1.68 ± 0.01 eV). Measured dissociation energies are used to derive heats of formation ΔfH0(Fe2+) = 1344 ± 2 kJ/mol, ΔfH0(Fe2) = 737 ± 2 kJ/mol, ΔfH0(Fe2−) = 649 ± 2 kJ/mol, ΔfH0(Fe2O+) = 1094 ± 2 kJ/mol, and ΔfH0(Fe2O2+) = 853 ± 21 kJ/mol. The Fe2O2+ ions studied here are determined to have a ring structure based on drift tube ion mobility measurements prior to their confinement in the cryogenic ion trap. The photodissociation measurements significantly improve the accuracy of basic thermochemical data for these small, fundamental iron and iron oxide clusters.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP41622K
Abstract: In this perspective article we describe recent infrared spectroscopic investigations of mass-selected M(+)-H(2) and M(+)-D(2) complexes in the gas-phase, with targets that include Li(+)-H(2), B(+)-H(2), Na(+)-H(2), Mg(+)-H(2), Al(+)-H(2), Cr(+)-D(2), Mn(+)-H(2), Zn(+)-D(2) and Ag(+)-H(2). Interactions between molecular hydrogen and metal cations play a key role in several contexts, including in the storage of molecular hydrogen in zeolites, metal-organic frameworks, and doped carbon nanostructures. Arguably, the clearest view of the interaction between dihydrogen and a metal cation can be obtained by probing M(+)-H(2) complexes in the gas phase, free from the complicating influences of solvents or substrates. Infrared spectra of the complexes in the H-H and D-D stretch regions are obtained by monitoring M(+) photofragments as the excitation wavelength is scanned. The spectra, which feature full rotational resolution, confirm that the M(+)-H(2) complexes share a common T-shaped equilibrium structure, consisting essentially of a perturbed H(2) molecule attached to the metal cation, but that the structural and vibrational parameters vary over a considerable range, depending on the size and electronic structure of the metal cation. Correlations are established between intermolecular bond lengths, dissociation energies, and frequency shifts of the H-H stretch vibrational mode. Ultimately, the M(+)-H(2) and M(+)-D(2) infrared spectra provide a comprehensive set of benchmarks for modelling and understanding the M(+)···H(2) interaction.
No related organisations have been discovered for Evan Bieske.
Start Date: 2009
End Date: 12-2013
Amount: $260,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2002
End Date: 12-2005
Amount: $270,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2016
End Date: 12-2023
Amount: $665,765.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2012
End Date: 11-2017
Amount: $480,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2008
End Date: 12-2010
Amount: $353,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2005
End Date: 12-2008
Amount: $310,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 10-2010
End Date: 12-2010
Amount: $200,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 01-2004
End Date: 12-2003
Amount: $10,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2015
End Date: 12-2019
Amount: $534,300.00
Funder: Australian Research Council
View Funded ActivityStart Date: 12-2003
End Date: 12-2004
Amount: $237,654.00
Funder: Australian Research Council
View Funded ActivityStart Date: 01-2004
End Date: 12-2009
Amount: $950,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2011
End Date: 12-2016
Amount: $715,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2013
End Date: 12-2014
Amount: $200,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2018
End Date: 12-2018
Amount: $563,390.00
Funder: Australian Research Council
View Funded Activity