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

Abstract

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.

Ab initio investigation of the CO–N2 quantum scattering: The collisional perturbation of the pure rotational R(0) line in CO

“…Finally, the first comprehensive database of the line-shape parameters (broadening, shift, their speed dependence and the complex Dicke parameter), generated from ab initio calculations, was reported in Ref. 117. The same methodology was applied to the cases of helium-perturbed lines of HD 118,119 and D 2 .…”

CO-Ar collisions: ab initio model matches experimental spectra at a sub percent level over a wide pressure range

“…The double-power-law (DPL) temperature dependence of the spectral line-shape parameters adopted in the HI-TRAN database [13,42] is defined by the following equation: TABLE IV. Line shape parameters for the pure rotational R(0) line of CO in argon and for selected temperatures: pressure broadening coefficients (γ0), pressure shift coefficients (δ0), real and imaginary parts of the complex Dicke parameter (νopt), and the real part of the line mixing coefficient (y).…”

“…The success of this approach was recently demonstrated by the example of the simplest cases corresponding to collisions of H 2 with He [11][12][13], HD with He [14] and D 2 with D 2 [10]. To advance further in this direction, the approach was recently used for the study of collisions between the CO molecule and Ar based on the shapes of two and five rovibrational transitions in the P branch of the fundamental and second-overtone bands, respectively [15,16].…”

Fully quantum calculations of O2–N2 scattering using a new potential energy surface: Collisional perturbations of the oxygen 118 GHz fine structure line

“…So far, in this context, extensive ab initio quantum-scattering calculations of the line-shape parameters were performed for the simple systems of He-perturbed H 2 [29][30][31][32][33] and HD 34,35 , which are relevant for the atmospheres of Solar System gas giants and some types of exoplanets. Recently, these results were used to generate comprehensive beyond-Voigt line-shape parameter dataset for these two systems 36,37 that are consistent with the HI-TRAN double-power-law representation. 38 Similar work is in progress for N 2 -perturbed CO, which is relevant for Earth's atmosphere; recently the first results were published in Ref.…”