Detailed knowledge of spectroscopic parameters for prominent Q branches of methane is necessary for interpretation and modeling of high resolution infrared spectra of terrestrial and planetary atmospheres. We have measured air-broadened line shape parameters in the Q branch of ¹²CH₄ in the ν₃ fundamental band for a large number of transitions in the 3000 to 3023 cm⁻¹ region by analyzing 13 room-temperature laboratory absorption spectra. Twelve of these spectra were recorded with 0.01 cm⁻¹ resolution using the McMath-Pierce Fourier transform spectrometer (FTS) of the National Solar Observatory (NSO) on Kitt Peak, and one higher-resolution ( ∼ 0.0011 cm⁻¹) low pressure ( ∼ 1 Torr) spectrum of methane was obtained using the Bruker IFS 120HR FTS at the Pacific Northwest National Laboratory (PNNL) in Richland, WA. The air-broadened spectra were recorded using various absorption cells with path lengths of 5, 20, 25, and 150 cm, total sample pressures between 50 and 500 Torr, and CH₄ volume mixing ratios of 0.01 or less. All 13 spectra were fit simultaneously covering the 3000-3023 cm⁻¹ spectral region using a multispectrum nonlinear least squares techniqueD. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith, D. Atkins, JQSRT 53 (1995) 705-721.o retrieve accurate line positions, absolute intensities, Lorentz air-broadened widths and pressure-shift coefficients. Line mixing using the off-diagonal relaxation matrix element formalismA. Levy, N. Lacome, C. Chackerian, Collisional line mixing, in Spectroscopy of the Earth′s Atmosphere and Interstellar Medium, Academic Press, Inc., Boston (1992) 261-337.as measured for a number of pairs of transitions for the CH₄-air collisional system. The results will be compared to values reported in the literature.

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D. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith, D. Atkins, JQSRT 53 (1995) 705-721.t A. Levy, N. Lacome, C. Chackerian, Collisional line mixing, in Spectroscopy of the Earth′s Atmosphere and Interstellar Medium, Academic Press, Inc., Boston (1992) 261-337.w

Several Doppler limited rotational transitions of methane induced by centrifugal distortion have been measured with an unprecedented frequency accuracy using the THz photomixing synthesizer based on a frequency comb. Compared to previous synchrotron based FT-Far-IR measurements of Boudon et al. V. Boudon, O. Pirali, P. Roy, J.-B. Brubach, L. Manceron, J. Vander Auwera, J. Quant. Spectrosc. Radiat. Transfer, 111, 1117-1129 (2010). the accuracy of the line frequency measurements is improved by one order of magnitude, this yields a corresponding increase of two orders of magnitude to the weighting of these transitions in the global fit. The rotational transitions in the ν₄←ν₄ hot band are measured for the first time by the broad spectral coverage of the photomixing CW-THz spectrometer providing access up to R(5) transitions at 2.6 THz. The new global fit including the present lines has been used to update the methane line list of the HITRAN database. Some small, but significant variations of the parameter values are observed and are accompanied by a reduction of the 1-σ uncertainties on the rotational (B₀) and centrifugal distortion (D₀) constants.

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V. Boudon, O. Pirali, P. Roy, J.-B. Brubach, L. Manceron, J. Vander Auwera, J. Quant. Spectrosc. Radiat. Transfer, 111, 1117-1129 (2010).,

Propane is one of several hydrocarbons present in the atmospheres of the Giant Planets, Jupiter and Saturn. In order to characterize the atmospheres of the Giant Planets, it is necessary to provide absorption cross sections which can be used to determine abundances. Absorption cross sections have been obtained from high resolution transmission spectra recorded at the Canadian Light Source Far Infrared beamline. The experimental conditions used mimic those of the atmospheres belonging to the Giant Planets using He and H₂ as foreign broadeners.

This is the first report in a project to record high resolution IR data of the ¹³C and D substituted isotopologues of propane. In this talk we will give details on the first high resolution (∆ν = 0.0009 cm⁻¹) IR investigation of 2-¹³C-propane. Spectra of the CCC skeletal bending mode near 336.767 cm⁻¹(B-type) and the wagging mode near 746.615 cm⁻¹(C-type) were recorded using the FTS on the Far-IR beamline of the Canadian Light Source (CLS). The spectra were assigned both traditionally and with the aid of the PGOPHER program of Colin Western.C. Western, J. Quant. Spectrosc. & Rad. Transf. 186, 221 ff. (2017).he only available MW data on this molecule are the six K =0 J lines from Lide.Lide, J.Chem. Phys. 33, p.1514ff. (1960).e therefore had to use the present data to determine a new set of ground state constants that included centrifugal distortion terms for this molecule. We compare these experimentally determined values with the recent ab initio values of Villa, Senent & Carvajal.Villa, Senent & Carvajal, PCCP 15, 10258 (2013).pper state constants for both bands have been found that provide a good simulation of the spectra. The hope is that this data will be useful in identifying isotopic propane lines in Titan and other astrophysical objects.

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C. Western, J. Quant. Spectrosc. & Rad. Transf. 186, 221 ff. (2017).T Lide, J.Chem. Phys. 33, p.1514ff. (1960).W Villa, Senent & Carvajal, PCCP 15, 10258 (2013).U

We report in this talk on the first high resolution IR spectra (∆ν = 0.0009 cm⁻¹) of the 1-¹³C-Propane isotopologue. Spectra were taken on the Bruker FTS instrument on the Far-IR beamline at the Canadian National Synchrotron (CLS) located at the University of Saskatchewan. The ν₉ B-type band centered near 366.404 cm⁻¹ appears unperturbed and lines were assigned up to K = 17 and J = 50. Since the 1960 MW study of LideLide, J. Chem. Phys. 33, p. 1514 ff. (1960)nly used 6 J lines of K = 0 we had to use GSCD analyses to determine a fuller set of molecular constants for this molecule. Since normal propane has been detected using the ν₂₆ C-type band in Titan and other astrophysical objects our main focus was on the analagous bands for the both the 1-¹³C and 2-¹³C isotopologues. Assigned lines up to K = 17, J = 50 in ν₂₆ were analyzed with GSCD to independently obtain ground state rotational constants. These were consistent with those obtained from the ν₉ analysis. Upper state constants were also determined that reproduce the vast majority of this band. As in the normal and 2-¹³C species a Coriolis resonance with the 2ν₉ state causes lines of most K levels above 15 to be shifted.Flaud, Kwabia Tchana, Lafferty & Nixon, Mol. Phys. 108, p. 699 ff. (2010)e did not have enough sample available at the time of these experiments to be able to record the 2ν₉ - ν₉ hot band transitions in the low frequency study of ν₉.

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Lide, J. Chem. Phys. 33, p. 1514 ff. (1960)o Flaud, Kwabia Tchana, Lafferty & Nixon, Mol. Phys. 108, p. 699 ff. (2010)W

This is is the first high resolution IR study of any band of the 2-¹³C-propene species. There have been only two previous high resolution studies of vibration-rotation bands of the normal species.Ainetschian, Fraser, Ortigoso & Pate, J. Chem. Phys. 100, 729 ff. (1994); Lafferty, Flaud & Herman, J. Mol. Struct. 780-781, 65 ff. (2006).he band examined here is the ν₁₄ (A') CCC skeletal bending near 421.847 cm⁻¹which has an A-Type asymmetric rotor structure. The spectra were recorded on the FTS at the Far-IR beamline of the Canadian Light Source with a resolution of ∆ν = 0.0009 cm⁻¹. We have assigned and fitted around 2200 transitions and determined ground and upper state rotational constants. Lines with J up to 49 and K up to 12 were included. The subbands with K greater than 12 were perturbed and show torsional splittings that vary from small to extremely large. The fitting was done with the PGOPHER program of Colin Western.Western, J. Quant. Spectrosc. Rad. Transf. 186, 221 ff. (2017).he GS constants are in good agreement with the MW constants reported recently by Craig, Groner and co-workers.Paper M109, 71st ISMS Symposium (2016); J. Mol. Spectrosc. 328, 1-6 (2016).html:<hr /><h3>Footnotes: Ainetschian, Fraser, Ortigoso & Pate, J. Chem. Phys. 100, 729 ff. (1994); Lafferty, Flaud & Herman, J. Mol. Struct. 780-781, 65 ff. (2006).T Western, J. Quant. Spectrosc. Rad. Transf. 186, 221 ff. (2017).T Paper M109, 71st ISMS Symposium (2016); J. Mol. Spectrosc. 328, 1-6 (2016).

The atmosphere of Venus is known to contain trace amounts of SO, SO₂, OCS, H₂SO₄, and possibly H₂S and elemental sulfur oligomers, S_n. Modeling studies indicate that many more compounds containing sulfur and both sulfur and chlorine may also be present, given that the known compounds are photolyzed by solar radiation in the upper atmosphere of Venus and yield reactive radical species. A large number of exotic compounds containing S, O, H, C, and/or Cl of suspected or plausible significance for Venus chemistry have been characterized at the RCCSD(T)/aug-cc-pVTZ level, yielding structures, dipole moments, and dipole polarizabilities. Representative compounds and associated chemical reactions will be discussed. Both abstraction and addition-elimination reactions have been characterized.

Carbon chains and derivatives are highly active species, which are widely existed as reactive intermediates in many chemical processes including atmospheric chemistry, hydrocarbon combustion, as well as interstellar chemistry. The carbon chain cations, HC_nO⁺ (n = 5-12) are produced via pulsed laser vaporization of a graphite target in supersonic expansions containing carbon monoxide and hydrogen. The infrared spectra are measured via mass-selected infrared photodissociation spectroscopy of the CO “tagged” [HC_nO·CO] cation complexes in the 1600-3500 cm⁻¹region. The geometries and electronic ground states of these cation complexes are determined by their infrared spectra in conjunction with theoretical calculations. All the HC_nO⁺ (n = 5-12) core cations are characterized to be linear carbon chain derivatives terminated by hydrogen and oxygen. The HC_nO⁺ cations with odd n have closed-shell singlet ground states with polyyne-like structures, while those with even n have triplet ground states with allene-like structures.

In this talk, we present the energetics and kinetics of the insertion reaction of the O(¹D) into the H₂CO₃ molecule that finally produces the percarbonic acid [H₂C(O)O₃] molecule (H₂CO₃ + O(¹D)→ H₂C(O)O₃). The rate constants have been calculated by the Variable-Reaction-Coordinate Variational Transition State Theory (VRC−VTST). From our results, we show that the rate constants of the insertion reaction are significantly higher than the rate constants associated with the H₂O-assisted H₂CO₃ decomposition (H₂CO₃ + H₂O → CO₂ + 2H₂O), acetic acid (AA)-assisted H₂CO₃ decomposition (H₂CO₃ + AA → CO₂ + H₂O + AA) and OH radical-initiated H₂CO₃ degradation reaction (H₂CO₃ + OH^. → HCO₃^. + H₂O) −which are currently assumed to be the potentially important reaction channels to interpret the atmospheric loss of the H₂CO₃ molecule in the Earth. Finally, we also discuss the potential impact of the H₂O-assisted H₂CO₃ decomposition reaction, OH radical-initiated H₂CO₃ degradation reaction and the above-mentioned insertion reaction on equal footing toward the loss of H₂CO₃ molecule, especially, in the surface of Mars.

In order to understand planetary climate systems, modeling the properties of atmospheric aerosols is vital. Aerosol formation plays an important role in planetary climates and is tied to feedback loops that can either warm or cool a planet. Sulfur compounds are known to play an important role in new particle aerosol formation and have been observed in a number of planetary atmospheres throughout our solar system. Our current understanding of sulfur chemistry explains much of what we observe in Earth’s atmosphere; however, several discrepancies arise when comparing observations of the Venusian atmosphere with model predictions. This suggests that there are still problems in our fundamental understanding of sulfur chemistry. This is concerning given recent renewed interest in sulfate injections in the stratosphere for solar radiation management geo-engineering schemes. We investigate the role of sunlight as a potential driver of the formation of sulfur-containing aerosols. I will present recent work investigating the generation of large quantities of aerosol from the irradiation of mixtures of SO₂ with water and organic species, using a solar simulator that mimics the light that is available in the Earth’s troposphere and the Venusian middle atmosphere. I will present on recent work done in our lab suggesting the formation of sulfurous acid, H₂SO₃, and describe experimental work that supports this proposed mechanism. Additionally I will present on new work showing the highly reactive nature of electronically excited SO₂ with saturated alkane species. The implications of this photochemically induced sulfur aerosol formation in the atmosphere of Earth and other planetary atmospheres will be discussed.