Ab initio line-shape calculations for the S and O branches of H2 perturbed by He

Jóźwiak, Hubert; Thibault, Franck; Stolarczyk, Nikodem; Wcisło, Piotr

doi:10.1016/j.jqsrt.2018.08.023

Cited by 22 publications

(37 citation statements)

References 24 publications

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“…Quantum-mechanical calculations of collisional dephasing have been performed for numerous systems [13,26], including CO-Ar [20,21,27,28]. In contrast, treatments accounting for both dephasing and the effects of VCs were mostly limited to the hydrogen molecule and its isotopologues [19,22,[29][30][31], which are not representative of systems relevant to atmospheric studies.…”

Section: Introductionmentioning

confidence: 99%

Subpercent agreement between ab initio and experimental collision-induced line shapes of carbon monoxide perturbed by argon

et al. 2020

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We present fully ab initio calculations of second-overtone rovibrational line shapes of carbon monoxide perturbed by argon. The quantum mechanical scattering problem between CO and Ar is solved numerically for two different ab initio interaction potentials. We use the generalized Hess method to determine spectroscopic cross sections which describe the effect of collisions on each spectral line. Using these cross sections, we determine the line-shape parameters that we use to generate the Hartmann-Tran and speed-dependent billiard ball profiles. We compare the generated line shapes with high-quality experimental line profiles of five lines measured at five pressures between 0.01 and 1 atm. A subpercent agreement over the entire pressure range is obtained. Calculations for the P(9) line are used to inspect the effects of the two interaction potentials. The discrepancies for both the considered interaction potentials and the experiment are explained within the described theoretical framework. The presented results are the most accurate collisional line-shape calculations for a system with collision dynamics representative of atmospherically relevant species.

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Section: Introductionmentioning

confidence: 99%

Subpercent agreement between ab initio and experimental collision-induced line shapes of carbon monoxide perturbed by argon

et al. 2020

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“…For the H 2 -He system, the PES is three-dimensional; i.e., it depends on the distance between the center of mass of the hydrogen molecule and the helium atom, R, the intramolecular distance, r, and the angle between the inter-and intramolecular axes, θ. To carry out the close-coupling quantum scattering calculations [66], the PES is projected on Legendre polynomials and averaged over the rovibrational wave functions of the hydrogen molecule [3,32]. The generalized spectroscopic cross-sections, σ q λ , for the electric quadrupole lines considered here (q = 2), as functions of the initial kinetic energy, E KIN , are determined from S-matrix elements [32,60,64].…”

Section: Methodsmentioning

confidence: 99%

“…To carry out the close-coupling quantum scattering calculations [66], the PES is projected on Legendre polynomials and averaged over the rovibrational wave functions of the hydrogen molecule [3,32]. The generalized spectroscopic cross-sections, σ q λ , for the electric quadrupole lines considered here (q = 2), as functions of the initial kinetic energy, E KIN , are determined from S-matrix elements [32,60,64]. For the zero rank of the velocity tensor, λ = 0, σ q λ reduces to the pressure broadening and shift cross-sections (PBXS and PSXS, respectively) [3,65,67,68], while for λ = 1 it provides the complex Dicke cross-section [31,32,59,60,64] (RDXS and IDXS for its real and imaginary parts, respectively).…”

Section: Methodsmentioning

confidence: 99%

“…The influence of the molecular hydrogen collisions, with perturbers such as H 2 isotopologues or noble gas atoms, on the shapes of the rotational and rovibrational lines in H 2 were already established in a wide range of temperatures from 20 K to 1200 K [20][21][22][23][24][25][26]. In particular, the effects of the H 2 -He collisions on the widths and shifts of H 2 rovibrational lines were subjected to intense experimental and theoretical studies [3,25,[27][28][29][30][31][32]. However, the collision-perturbed line profiles calculated from first principles never reached agreement with experimental data at the subpercent level.…”

Section: Introductionmentioning

confidence: 99%

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H2-He collisions:Ab initiotheory meets cavity-enhanced spectra

et al. 2020

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Fully quantum ab initio calculations of the collision-induced shapes of two rovibrational H2 lines perturbed by He provide an unprecedented subpercent agreement with ultra-accurate cavity-enhanced measurements. This level of consistency between theory and experiment hinges on a highly accurate potential energy surface and a realistic treatment of the velocity changing and dephasing collisions. In addition to the fundamental importance, these results show that ab initio calculations can provide reference data for spectroscopic studies of planet atmospheres at the required accuracy level and can be used to populate spectroscopic line-by-line databases.

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“…We extend the calculations of the generalized spectroscopic cross sections reported in Refs. [15,26] by taking into account the centrifugal distortion for all the bands and by including the hot bands. We extrapolate the ab initio results to populate very weak lines, i.e., higher overtones, v ≥ 6, higher rotational numbers, J ≥ 8, and high-v hot bands, v ≥ 6; following the standard HITRAN notation, we denote the final and initial states of a transition with primes and double primes, respectively.…”

Section: Introductionmentioning

confidence: 99%

The first comprehensive dataset of beyond-Voigt line-shape parameters from ab initio quantum scattering calculations for the HITRAN database: He-perturbed H2 case study

Wcisło

Thibault

Stolarczyk

et al. 2021

Journal of Quantitative Spectroscopy and Radiative Transfer

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We demonstrate a new method for populating line-by-line spectroscopic databases with beyond-Voigt line-shape parameters, which is based on ab initio quantum scattering calculations. We report a comprehensive dataset for the benchmark system of He-perturbed H2 (we cover all the rovibrational bands that are present in the HITRAN spectroscopic database). We generate the entire dataset of the line-shape parameters (broadening and shift, their speed dependence, and the complex Dicke parameter) from fully ab initio quantum-scattering calculations. We extend the previous calculations by taking into account the centrifugal distortion for all the bands and by including the hot bands. The results are projected on a simple structure of the quadratic speed-dependent hard-collision profile. We report a simple and compact formula that allows the speed-dependence parameters to be calculated directly from the generalized spectroscopic cross sections. For each line and each lineshape parameter, we provide a full temperature dependence within the double-power-law (DPL) representation, which makes the dataset compatible with the HITRAN database. The temperature dependences cover the range from 20 to 1000 K, which includes the low temperatures relevant for the studies of the atmospheres of giant planets. The final outcome from our dataset is validated on highly accurate experimental spectra collected with cavity ring-down spectrometers. The methodology can be applied to many other molecular species important for atmospheric and planetary studies.

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Ab initio line-shape calculations for the S and O branches of H2 perturbed by He

Abstract: Highlights• Close-coupling calculations of pressure broadening and shifting coefficients • Close-coupling calculations of Dicke parameters • Data for anisotropic Raman S (j=0-5) and O (j=2-5) lines for purely rotational transitions, fundamental band and first four overtones

Cited by 22 publications

References 24 publications

Subpercent agreement between ab initio and experimental collision-induced line shapes of carbon monoxide perturbed by argon

Subpercent agreement between ab initio and experimental collision-induced line shapes of carbon monoxide perturbed by argon

H2-He collisions:Ab initiotheory meets cavity-enhanced spectra

The first comprehensive dataset of beyond-Voigt line-shape parameters from ab initio quantum scattering calculations for the HITRAN database: He-perturbed H2 case study

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