In the physical conditions of the troposphere, Carbonyl sulphide (
16
O
12
C
32
S) and Argon (Ar) are present. In the goal of studying the rate coefficients for rotational excitations of OCS with an ...abundant element in the troposphere, such as Ar, a new potential energy surface (PES) of OCS-Ar system over their ground electronic states: OCS (
X
1
Σ
+
) and Ar(
S
u
1
), has been investigated with the ab initio explicitly correlated Coupled Cluster including single, double and perturbative treatment of triple excitations (CCSD(T)-F12) level of theory, associated to the augmented correlation consistent valence triple zeta Aug-cc-pVTZ basis set. In this paper, the Coupled State approximate method “CS” was used in order to calculate inelastic cross-sections at energies up to
2000
cm
−
1
. The collisional rate coefficients derived from these rotational inelastic cross-sections were determined and discussed for kinetic temperature
T
≤
400
K
and for OCS rotational levels
J
≤
20
.
For some temperatures of atmospheric interest from 200 to 298 K, the self-broadening coefficients of OCS-OCS and HCN-HCN collisional systems, at different strengths of electrostatic interactions, ...were calculated respectively for ν
and ν
bands for a wide range of rotational quantum numbers J. In particular, we have considered some lines that were not studied previously. We have employed the approximation of bi-resonance functions (Starikov, 2012) in the frame of the semiclassical model of Robert and Bonamy with exact trajectory (RBE). The calculated results are found to be fully consistent with the available experimental values of self-broadening coefficients of OCS and HCN. A comparative study shows that the RBE calculations reproduce the dependence of broadening coefficients on quantum number J much better than the simpler Robert and Bonamy model with parabolic trajectory (RB) for all considered temperatures.
•N2-broadening coefficients for transitions in the ν6 vibrational band of CH3F have been calculated.•The Robert and Bonamy semi-classical formalism with parabolic and exact trajectories was ...used.•Temperature dependence exponents n for transitions in the ν6 band were computed for J up to 60 and K up to 10.•Temperatures from 296 K down to 183 K have been considered.
Using Robert and Bonamy formalism (with parabolic and exact trajectories) based on the semi-classical impact theory, N2-broadening coefficients of methyl fluoride CH3F were calculated for transitions belonging to the PP-, PQ-, PR-, RP-, RQ- and RR- sub-branches of the ν6 perpendicular band near 8.5 µm. The calculations showed the predominance of the dipole–quadruple interaction. The J and K rotational quantum numbers dependencies of the computed coefficients that are consistent with previous measurements were clearly observed in this study. For a fixed value of J, we noticed a decrease in the broadening coefficients, which was more significant at lower J values.
In order to deduce the temperature exponent, the N2-broadening coefficients of CH3F were calculated at various temperatures of atmospheric interest between 183 and 296 K with J ≤ 60 and K ≤ 10. These exponents were, in general, J-dependent and K-independent, except for K close to J.
Using Fourier transform spectrometer, He-broadening coefficients in the
and
bands of carbonyl sulfide (
16
O
12
C
32
S) have been measured for the first time in the P- and R-branches. Measurements ...have been performed at room temperature (295 K) for 200 ro-vibrational lines with rotational quantum number ranging from 1 ≤ J ≤ 64, using a mono-spectrum non-linear least squares fitting of Voigt profiles. The measured values were discussed as a function of the rotational quantum number and compared to previous data. These broadening coefficients were also calculated on the basis of Robert and Bonamy's formalism using an ab-initio potential energy surface (PES). In addition, we have measured pressure shift coefficients for 92 transitions in both bands, these results were compared with those of the 2ν
3
band. The line intensities in the
and
bands were also retrieved using the same spectra. The analysis of these intensities allows us to derive a consistent set of line intensity parameters such as vibrational transition moments, band intensities as well as Herman-Wallis (HW) coefficients.
Using Fourier transform spectrometer, He-broadening coefficients have been measured for the first time in the P and R branches of the 2ν1 parallel band of carbonyl sulfide (OCS). The measurements ...have been performed at room temperature for rotational quantum number up to J = 70. A total of 131 lines were measured using a nonlinear least squares multi-pressure spectrum fitting procedure. Since the measurements have been performed using different values of OCS pressures, we have also retrieved line intensities of the ro-vibrational lines of the same branches. The fits were performed using the Voigt profile which leads to a precise determination of these spectroscopic parameters.
From line intensities, we have determined vibrational transition moment, band intensity as well as Herman-Wallis parameters for the 2ν1 band. The results have been discussed as a function of the rotational quantum number and compared to previous data.
The line-mixing effect on broadening coefficients was also analyzed showing a negligible influence.
•He-broadening have been measured for the first time for 131 lines in the 2ν1 of OCS.•The results have been discussed as a function of J and K and branch.•Line intensities, vibrational transition moment, band intensity, and Herman-Wallis parameters have been determined.•The line-mixing effect on broadening coefficients was analyzed.
•High-resolution lines of H2S self-perturbed and perturbed by N2 have been recorded at room temperature using a frequency modulated THz spectrometer.•The self- and N2-broadening coefficients of H2S ...of pure rotational transitions have been retrieved in the submillimeter region.•The lineshapes are well reproduced by the Speed-Dependent Voigt profile accounting for the speed dependence of relaxation rates.•The broadening coefficients were calculated with the Robert and Bonamy formalism.•The observed J″ and Ka″ rotational dependences have been analyzed using an empirical model and compared to previous rovibrational studies.
High-resolution lines of H2S self-perturbed and perturbed by N2 have been recorded at room temperature using a frequency modulated THz spectrometer at pressures of H2S ranging from 0.1 to 1.0 mbar. A non-linear least squares fitting of these spectra has been performed to retrieve self- and N2-broadening coefficients of pure rotational transitions (mainly in the RQ sub-branch) of H2S in the submillimeter region. We show that the lineshapes are well reproduced by the Speed-Dependent Voigt profile accounting for the speed dependence of relaxation rates which display linear pressure dependencies. Using the Robert and Bonamy formalism, these coefficients were calculated, showing the need to account for all contributions of the intermolecular interaction for N2-broadening. The calculated coefficients are consistent with the measured data and the average accuracy of the line parameters has been estimated to be about 5%. The observed J″ and Ka″ rotational dependences have been analyzed using an empirical model and compared to previous rovibrational studies in the ν2 fundamental band. In our study the self- and the N2-broadening coefficients decreases monotonically with Ka″ and J″, respectively.
Comparison between measured 9 and theoretical (present work) self-broadening coefficients of the ν2 band of HCN. The experimental values at temperatures 267K, 232K and 212K were deduced using Eq. ...(16) and measured values of n exponent of Ref. 9. Display omitted
•Self line broadening coefficients for transitions in the ν1 and ν2 vibrational bands of OCS and HCN have been calculated.•Temperatures from 298K down to 200K have been considered.•The Robert and Bonamy semi-classical formalism with exact trajectories was used.•Approximation of bi-resonances functions of Starikov 1 was employed in the theoretical calculations.•Temperature dependence exponents n for transitions in the ν2 vibrational band of HCN were computed.
For some temperatures of atmospheric interest from 200 to 298K, the self-broadening coefficients of OCS-OCS and HCN-HCN collisional systems, at different strengths of electrostatic interactions, were calculated respectively for ν1 and ν2 bands for a wide range of rotational quantum numbers J. In particular, we have considered some lines that were not studied previously. We have employed the approximation of bi-resonance functions (Starikov, 2012) in the frame of the semiclassical model of Robert and Bonamy with exact trajectory (RBE).
The calculated results are found to be fully consistent with the available experimental values of self-broadening coefficients of OCS and HCN. A comparative study shows that the RBE calculations reproduce the dependence of broadening coefficients on quantum number J much better than the simpler Robert and Bonamy model with parabolic trajectory (RB) for all considered temperatures.
In this paper, we report measured Rosenkranz N sub(2)- and O sub(2)-broadening, induced pressure-shift and mixing coefficients for OCS in the nu sub(1) + nu sub(3) band, using a multi-pressure ...fitting technique applied to the measured shapes of the lines, including the interference effects caused by the line overlaps. These measurements were made by analysing six laboratory absorption spectra recorded at 0.004 cm super(-1) resolution using the Fourier transform spectrometer Bruker IFS125HR located at the Laboratoire Interuniversitaire des Systemes Atmospheriques, in Creteil. The spectra have been recorded in the 1850-3000 cm super(-1) wave number range at 295 K, using a multipass absorption cell with an optical path of 3.249 m. The total sample pressures ranged from 5.97 to 83.28 Torr with OCS volume mixing ratios between 0.001 and 0.013 in nitrogen or oxygen. We have been able to determine the N sub(2)- and O sub(2)-pressure-broadening coefficients of 81 nu sub(1) + nu sub(3) transitions with rotational quantum number J up to 50. The measured N sub(2)- and O sub(2)-broadening coefficients range from 0.0815 plus or minus 0.0698 to 0.1169 plus or minus 0.1027 cm super(-1) atm super(-1) at 295 K, respectively. Most of the measured pressure shifts are positive. The reported N sub(2)- and O sub(2)-induced pressure-shift coefficients vary from about -0.0103 plus or minus 0.0092 to 0.0097 plus or minus 0.0092 cm super(-1) atm super(-1), respectively. We have examined the dependence of the measured broadening parameters on the quantum number m (m = -J for the P branch and m = J + 1 for the R branch) and also developed an empirical expression to describe the broadening coefficients in terms of |m|. On average, this empirical expression reproduces the measured broadening coefficients to within 2%. Using a semi-classical Robert and Bonamy formalism, the theoretical broadening coefficients have been calculated at room temperature and compared with the experimental results. The theoretical results of the broadening coefficients are in very good overall agreement with the experimental data (2%).
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