ORCID Profile
0000-0002-3994-1276
Current Organisation
University of New South Wales
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Structural Chemistry and Spectroscopy | Environmental Chemistry (incl. Atmospheric Chemistry) | Physical Chemistry (Incl. Structural)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Atmospheric Processes and Dynamics |
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CP00651F
Abstract: Rotational spectra have been measured and assigned for four conformers of trans -urocanic acid.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CP03557D
Abstract: A clear dispersion-enhanced preference for OH–π binding over the competing and more intuitive OH–O binding motif is observed.
Publisher: AIP Publishing
Date: 12-2017
DOI: 10.1063/1.5002662
Abstract: The combination of halogen- and hydrogen-bonding capabilities possessed by 4-bromopyrazole and 4-iodopyrazole has led to them being described as “magic bullets” for biochemical structure determination. Laser vaporisation was used to introduce each of these 4-halopyrazoles into an argon gas s le undergoing supersonic expansion prior to the recording of the rotational spectra of these molecules by chirped-pulse Fourier transform microwave spectroscopy. Data were obtained for four isotopologues of 4-bromopyrazole and two isotopologues of 4-iodopyrazole. Isotopic substitutions were achieved at the hydrogens attached to the pyrrolic nitrogen atoms of both 4-halopyrazoles and at the bromine atom of 4-bromopyrazole. The experimentally determined nuclear quadrupole coupling constants, χaa(X) and χbb(X)−χcc(X), of the halogen atoms (where X is the halogen atom) of each molecule are compared with the results of the ab initio calculations and those for a range of other halogen-containing molecules. It is concluded that each of 4-bromopyrazole and 4-iodopyrazole will form halogen bonds that are broadly comparable in strength to those formed by CH3X and CF3X.
Publisher: Wiley
Date: 06-04-2016
Abstract: Molecular recognition of carbohydrates plays an important role in nature. The aggregation of the smallest sugar, glycolaldehyde, was studied in a conformer-selective manner using high-resolution rotational spectroscopy. Two different dimer structures were observed. The most stable conformer reveals C2 -symmetry by forming two intermolecular hydrogen bonds, giving up the strong intramolecular hydrogen bonds of the monomers and thus showing high hydrogen bond selectivity. By analyzing the spectra of the (13) C and (18) O isotopologues of the dimer in natural abundance, we could precisely determine the heavy backbone structure of the dimer. Comparison to the monomer structure and the complex with water provides insight into intermolecular interactions. Despite hydrogen bonding being the dominant interaction, precise predictions from quantum-chemical calculations highly rely on the consideration of dispersion.
Publisher: AIP Publishing
Date: 20-12-2017
DOI: 10.1063/1.5008744
Abstract: The rotational spectra of H3N⋯AgI and H2O⋯AgI have been recorded between 6.5 and 18.5 GHz by chirped-pulse Fourier-transform microwave spectroscopy. The complexes were generated through laser vaporisation of a solid target of silver or silver iodide in the presence of an argon gas pulse containing a low concentration of the Lewis base. The gaseous s le subsequently undergoes supersonic expansion which results in cooling of rotational and vibrational motions such that weakly bound complexes can form within the expanding gas jet. Spectroscopic parameters have been determined for eight isotopologues of H3N⋯AgI and six isotopologues of H2O⋯AgI. Rotational constants, B0 centrifugal distortion constants, DJ, DJK or ΔJ, ΔJK and the nuclear quadrupole coupling constants, χaa(I) and χbb(I) − χcc(I) are reported. H3N⋯AgI is shown to adopt a geometry that has C3v symmetry. The geometry of H2O⋯AgI is Cs at equilibrium but with a low barrier to inversion such that the vibrational wavefunction for the v = 0 state has C2v symmetry. Trends in the nuclear quadrupole coupling constant of the iodine nucleus, χaa(I), of L⋯AgI complexes are examined, where L is varied across the series (L = Ar, H3N, H2O, H2S, H3P, or CO). The results of experiments are reported alongside those of ab initio calculations at the CCSD(T)(F12*)/AVXZ level (X = T, Q).
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CP02876D
Abstract: High resolution rotational spectroscopy is used to map the conformational landscape and derive conformational relaxation pathways of citronellal.
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B905424N
Abstract: Aerosols of ozone have been generated in a collisional cooling cell and observed over a small temperature range via FTIR spectroscopy, with the phase transition from the vapour taking place in the range 80-84 K. The condensed phase bands at 1038 cm(-1) (nu3) and 2105 cm(-1) (nu1+nu3) were assigned to the liquid phase. Aerosols were also generated from mixtures of ozone and HCl. In the presence of liquid ozone aerosols, evidence of solvated HCl was observed via a broad IR band 2795 cm(-1). Notably, production of a metastable, amorphous solid phase of HCl (exhibiting a narrow band at 2780 cm(-1)) was favoured to the extent that it could be generated in large excess over the crystalline orthorhombic form that usually dominates at 80 K.
Publisher: Elsevier BV
Date: 09-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CP04104A
Abstract: We report on a detailed multi-spectroscopic analysis of the structures and internal dynamics of diphenylether and its aggregates with up to three water molecules by employing molecular beam experiments.
Publisher: Walter de Gruyter GmbH
Date: 11-09-2015
Abstract: The rotational spectra of the two structurally related molecules, 1,4-cineole and 1,8-cineole (eucalyptol), were measured between 2–8.5 GHz with chirped pulse Fourier transform microwave spectroscopy. The structures of these two molecules only differ in the connectivity of an ether functional group. This results in a significant change in the three dimensional structure of the molecule and consequently large differences in the rotational spectra. Only one conformer of each molecule was detected in the molecular jet and no line splittings due to internal rotations were detected. A substitution structure ( r s ) was determined for eucalyptol and benchmarked to quantum chemical structures allowing for a comparison of eucalyptol and 1,4-cineole.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5CP02582F
Abstract: The precise structure of the odourant molecule trans -cinnamaldehyde was determined using microwave spectroscopy by exploiting its high resolution and sensitivity.
Publisher: AIP Publishing
Date: 02-06-2015
DOI: 10.1063/1.4921833
Abstract: We apply chirality sensitive microwave three-wave mixing to 4-carvomenthenol, a molecule previously uncharacterized with rotational spectroscopy. We measure its rotational spectrum in the 2-8.5 GHz range and observe three molecular conformers. We describe our method in detail, from the initial step of spectral acquisition and assignment to the final step of determining absolute configuration and enantiomeric excess. Combining fitted rotational constants with dipole moment components derived from quantum chemical calculations, we identify candidate three-wave mixing cycles which were further tested using a double resonance method. Initial optimization of the three-wave mixing signal is done by varying the duration of the second excitation pulse. With known transition dipole matrix elements, absolute configuration can be directly determined from a single measurement.
Publisher: American Chemical Society (ACS)
Date: 15-07-2014
DOI: 10.1021/JP500811W
Publisher: AIP Publishing
Date: 03-12-2012
DOI: 10.1063/1.4768417
Abstract: High resolution FTIR spectra of 13C enriched tetrafluoroethylene (C2F4) were measured at 150 K at the Australian Synchrotron. Rovibrational transitions were assigned in the a-type symmetric and b-type antisymmetric CF2 stretches of 12C13CF4 and 13C2F4 near 1170 cm−1 and 1300 cm−1, respectively. Ground vibrational state spectroscopic constants for both molecules were determined in addition to the upper state constants for ν11 and ν9 of 13C2F4 and ν11, ν2+ν6, and ν5 of 12C13CF4. The ground state constants, along with those determined for the 12C2F4 isotopologue from previously published data, were used to determine a semi-experimental re structure rCC = 132.36 ± 0.37 pm, rCF = 131.11 ± 0.23 pm, αFCC = 123.3 ± 0.3° in excellent agreement with ab initio structures. Lower resolution FTIR spectra were measured between 100 and 5000 cm−1 at room temperature and band centres obtained for all modes of the three isotopologues although only 5 out of 12 modes in 12C2F4 and 13C2F4 are infrared (IR) active, the others were inferred from combination and hot-band positions. A number of modes are observed to be infrared active only in the 12C13CF4 isotopologue due to its lower symmetry. Most notably, decoupling of the antisymmetric CF2 motions in the two halves of 12C13CF4 results in 2 strongly IR active modes that involve motion at one carbon or the other.
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B905425C
Abstract: Aerosol particles of hydrogen chloride corresponding to three distinct solid phases have been generated in a collisional cooling cell and observed via FTIR spectroscopy. The cubic phase of HCl was observed with cell temperatures of 90-100 K, while the highly ordered orthorhombic phase predominated below this temperature. The previously reported metastable phase was also observed under some conditions. Density functional theory calculations at the B3LYP/6-311+G(d,p) level were performed on HCl clusters with a planar, zig-zag arrangement. Computed IR spectra for chain lengths up to 15 converge to show a band shape that is characteristic of the orthorhombic HCl phase. Injection of water along with HCl was found to have little influence on the formation of HCl particles. The reaction between HCl and NH3 to produce NH4Cl particles was also examined and found to occur over a wide range of temperatures (80-300 K). The formation of homogenous particles of HCl and NH3 competed with this chemical reaction as the cell temperature was lowered and when higher pressures of N2 buffer gas were used.
Publisher: Wiley
Date: 19-10-2018
Publisher: American Astronomical Society
Date: 20-09-2012
Publisher: AIP Publishing
Date: 08-10-2019
DOI: 10.1063/1.5119997
Abstract: The rotational spectra of N-, 2-, 4-, and 5-methylimidazole are reported and analyzed. Liquid N-methylimidazole was vaporized from a reservoir, and each of 2-, 4-, and 5-methylimidazole was laser-vaporized from a solid target prior to mixing with argon buffer gas and undergoing supersonic expansion from a pulsed nozzle. The spectra were recorded by chirped-pulse Fourier transform microwave spectroscopy in the 7.0–18.5 GHz frequency range. Rotational constants, A0, B0, and C0, centrifugal distortion constants, DJ, DJK, DK, d1, and d2, and nuclear quadrupole coupling constants of nitrogen atoms, χaa(N1), χbb(N1) − χcc(N1), χaa(N3), and χbb(N3) − χcc(N3), are determined from experimentally measured transition frequencies. Data recorded for isotopologues containing 13C or 15N are used to determine the rs coordinates of all heavy atoms in N-, 2-, and 4-methylimidazole. The results allow fitting of parameters in the Hamiltonian that describes internal rotation of the CH3 group about its local C3 axis. The V3 terms in the periodic potential energy functions that describe the internal rotation in N-, 2-, 4-, and 5-methylimidazole are determined to be 185.104(11), 122.7529(38), 317.20(14), and 386.001(19) cm−1, respectively, by the internal axis method. The experiments are supported by density functional theory calculations. Observed variations in barrier height are explained with reference to the symmetry of overlap between a π-like orbital on the CH3 group and π-orbitals on the aromatic ring.
Publisher: Elsevier BV
Date: 08-2015
Publisher: American Chemical Society (ACS)
Date: 25-03-2014
DOI: 10.1021/JP501302Q
Abstract: The IR spectrum of dichlorodifluoromethane (i.e., R12 or Freon-12) is central to its role as a major greenhouse contributor. In this study, high-resolution (0.000 96 cm(-1)) Fourier transform infrared spectra have been measured for R12 s les either cooled to around 150 K or at ambient temperature using facilities on the infrared beamline of the Australian Synchrotron. Over 14,000 lines of C(35)Cl2F2 and C(35)Cl(37)ClF2 were assigned to the b-type ν2 band centered around 668 cm(-1). For the c-type ν8 band at 1161 cm(-1), over 10,000 lines were assigned to the two isotopologues. Rovibrational fits resulted in upper state constants for all these band systems. Localized avoided crossings in the ν8 system of C(35)Cl2F2, resulting from both a direct b-axis Coriolis interaction with ν3 + ν4 + ν7 and an indirect interaction with ν3 + ν4 + ν9, were treated. An improved set of ground state constants for C(35)Cl(37)ClF2 was obtained by a combined fit of IR ground state combination differences and previously published millimeter wave lines. Together these new sets of constants allow for accurate prediction of these bands and direct comparison with satellite data to enable accurate quantification.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 05-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CP04315E
Abstract: The structure and properties of a gas phase complex formed between urea and isocyanic acid are characterised through microwave spectroscopy and ab initio calculations at the CCSD(T)(F12*)/aug-cc-pVTZ level.
Publisher: Wiley
Date: 05-09-2014
Abstract: Heavy-metal containing chiral compounds have been suggested as promising candidates for studying parity-violation effects. We report herein the broadband rotational spectroscopy study of the chiral complex [CpRe(CH3)(CO)(NO)] in the gas phase. The spectra obtained are very rich due to the two rhenium isotopologues ((185)Re and (187)Re), hyperfine structure arising from the rhenium and nitrogen nuclei, and the asymmetry of the chiral complex. Since rhenium is located very close to the molecular center of mass, the rotational constants for the two rhenium isotopologues are very similar. However they can be differentiated by their characteristic nuclear quadrupole hyperfine splitting patterns. Comparison with calculated nuclear quadrupole coupling constants shows that all-electron relativistic basis sets are necessary for a correct description of the rhenium atom in this type of complex. The present study is an important step towards future precision studies on chiral molecules.
Publisher: AIP Publishing
Date: 18-11-2016
DOI: 10.1063/1.4967477
Abstract: Complexes formed between H2S and each of CuI, AgI, and AuI have been isolated and structurally characterised in the gas phase. The H2S⋯MI complexes (where M is the metal atom) are generated through laser vaporisation of a metal rod in the presence of a low concentration of H2S and CF3I in a buffer gas of argon undergoing supersonic expansion. The microwave spectra of six isotopologues of each of H2S⋯CuI, H2S⋯AgI and three isotopologues of H2S⋯AuI have been measured by chirped-pulse Fourier transform microwave spectroscopy. The spectra are interpreted to determine geometries for the complexes and to establish the values of structural parameters. The complexes have Cs symmetry at equilibrium and have a pyramidal configuration about the sulfur atom. The local C2 axis of the hydrogen sulfide molecule intersects the linear axis defined by the three heavy atoms at an angle, ϕ = 75.00(47)° for M = Cu, ϕ = 78.43(76)° for M = Ag, and ϕ = 71.587(13)° for M = Au. The trend in the molecular geometries is consistent with significant relativistic effects in the gold-containing complex. The force constant describing the interaction between the H2S and MI sub-units is determined from the measured centrifugal distortion constant, ΔJ, of each complex. Nuclear quadrupole coupling constants, χaa(M) and χaa(I) (where M denotes the metal atom), are determined for H2S⋯CuI and H2S⋯AuI for the first time.
Publisher: American Astronomical Society
Date: 11-06-2012
Publisher: AIP Publishing
Date: 27-02-2019
DOI: 10.1063/1.5085281
Abstract: Ground-state rotational spectra were observed for ten symmetric-top isotopologues H3N⋯S=C=S, H3N⋯34S=C=S, H3N⋯S=C=34S, H3N⋯S=13C=S, H315N⋯S=C=S, H315N⋯34S=C=S, H315N⋯S=C=34S, H315N⋯S=13C=S, H315N⋯33S=C=S, and H315N⋯S=C=33S, the first five in their natural abundance in a mixture of ammonia and carbon disulphide in argon and the second group with enriched 15NH3. The four asymmetric-rotor isotopomers H2DN⋯S=C=S, H2DN⋯34S=C=S, H2DN⋯S=C=34S, and HD2N⋯S=C=S were investigated by using a s le composed of ND3 mixed with CS2. Rotational constants, centrifugal distortion constants, and 33S nuclear quadrupole coupling constants were determined from spectral analyses and were interpreted with the aid of models of the complex to determine its symmetry, geometry, one measure of the strength of the intermolecular binding, and information about the subunit dynamics. The complex has C3v symmetry, with nuclei in the order H3N⋯S=C=S, thereby establishing that the non-covalent interaction is a chalcogen bond involving the non-bonding electron pair of ammonia as the nucleophile and the axial region near one of the S atoms as the electrophile. The small intermolecular stretching force constant kσ = 3.95(5) N m−1 indicates a weak interaction and suggests the assumption of unperturbed component geometries on complex formation. A simple model used to account for the contribution of the subunit angular oscillations to the zero-point motion leads to the intermolecular bond length r(N⋯S) = 3.338(10) Å.
Publisher: Wiley
Date: 02-2017
DOI: 10.1002/HC.21361
Publisher: Wiley
Date: 19-10-2018
Abstract: Ice and solid H
Publisher: Elsevier BV
Date: 06-2019
Publisher: American Chemical Society (ACS)
Date: 06-11-2014
DOI: 10.1021/JP5087784
Abstract: Five intense bands of dichlorodifluoromethane (CFC-12, or R12) in the infrared atmospheric window help make it a major greenhouse contributor. These include the ν1 fundamental at 1101.4 cm(-1) and the ν2 + ν3 combination at 1128.6 cm(-1). High-resolution spectra measured using the Australian Synchrotron Far-Infrared beamline were analyzed, and transitions of C(35)Cl2F2 were assigned to ν1, ν2 + ν3, and the ν3 + 2ν5 combination at 1099.7 cm(-1). The (v3 = 1 v5 = 2) state couples indirectly to v1 = 1 via Fermi resonances linking both states with v2 = v3 = 1. The v1 = 1 rotational levels are further riddled with perturbations and avoided crossings due to Coriolis resonance with the upper vibrational states of ν2 + ν9 at 1102.4 cm(-1) and (indirectly) ν2 + ν7 at 1105.8 cm(-1). A global treatment of all these states fits the observed line positions and satisfactorily accounts for the significant intensity of ν2 + ν3. Spectral simulations elucidate resonance perturbations that affect the distribution of IR absorption in the CF stretch region, and consequently the global warming potential of R12. Combination levels derived from rovibrational analysis lead to reassessment of the gas phase wavenumber values for the ν3 (458.6 cm(-1)), ν7 (437.7 cm(-1)) and ν9 (436.9 cm(-1)) fundamentals of C(35)Cl2F2, consistent with a cold, vapor phase far IR spectrum and previously published solid state spectra. B3LYP and MP2 anharmonic frequency calculations provide further support. At the MP2/aug-cc-pVTZ level, the root mean square (r.m.s.) error for unscaled anharmonic fundamentals is 6.2 cm(-1), decreased to 1.7 cm(-1) if only considering the seven lowest wavenumber modes, and integrated band intensities according with experimental literature values. Smaller basis sets produce band strengths that are too high. Low-resolution band assignments are reported for C(35)Cl(37)ClF2, C(37)Cl2F2, and (13)C(35)Cl2F2.
Publisher: AIP Publishing
Date: 16-06-2011
DOI: 10.1063/1.3597775
Abstract: High resolution FTIR spectra of the short lived species ketenimine have been recorded in the regions 390–1300 cm−1 and 20–110 cm−1 using synchrotron radiation. Two thousand six hundred sixty transitions of the ν7 band centered at 693 cm−1 and 126 far-IR rotational transitions have been assigned. Rotational and centrifugal distortion parameters for the ν7 mode were determined and local Fermi and b-axis Coriolis interactions with 2ν12 are treated. A further refinement of the ground state, ν12 and ν8 parameters was also achieved, including the treatment of previously unrecognized ac-axis and ab-axis second order perturbations to the ground state.
Publisher: American Chemical Society (ACS)
Date: 08-01-2016
DOI: 10.1021/ACS.JPCLETT.5B02443
Abstract: broadband microwave spectroscopy is a proven tool to precisely determine molecular properties of gas-phase molecules. Recent developments make it applicable to investigate chiral molecules. Enantiomers can be differentiated, and the enantiomeric excess and, indirectly, the absolute configuration can be determined in a molecule-selective manner. The resonant character and high resolution of rotational spectroscopy provide a unique mixture compatibility. Future directions, such as extending the technique to chemical analysis, are discussed.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP43974G
Abstract: Mid-infrared spectra have been measured for cubic ice (I(c)) nanoparticles (3-150 nm diameter) formed by rapid collisional cooling over a wide range of temperatures (5-209 K). Spectral diagnostics, such as the ratio of surface related dangling OH to interior H-bonded OH stretch bands, reveal the manner in which particle size depends on bath gas temperature and density, and on water molecule concentration. For particles smaller than 5 nm strained intermolecular bonds on the surface and subsurface cause the predominant OH stretch peak position to be dramatically blue shifted by up to 40 cm(-1). In the size regime of 8-200 nm the position of the OH stretch absorption band maximum is relatively unaffected by particle size and it is possible to measure the temperature dependence of the peak location without influences from the surface or scattering. The band maximum shifts in a linear fashion from 3218 cm(-1) at 30 K to 3253 cm(-1) at 209 K, which may assist with temperature profiling of ice particles in atmospheric clouds and extraterrestrial systems. Over the same temperature range the librational mode band shifts very little, from 870 to 860 cm(-1). In the water stretching and bending regions discrete spectral features associated with the surface or sub-surface layers have been detected in particles as large as 80 nm.
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2018
End Date: 2020
Funder: Australian Research Council
View Funded ActivityStart Date: 12-2018
End Date: 06-2022
Amount: $353,700.00
Funder: Australian Research Council
View Funded Activity