Prediction of line shape parameters and their temperature dependences for CO 2 –N 2 using molecular dynamics simulations

International audienceWe show in this paper that requantized classical molecular dynamics simulations (rCMDS) are capable to predict various refined spectral-shape parameters of absorption lines with high precision. These simulations were performed for the CO2-N2 system. Combining classical molecular dynamics simulations and a requantization procedure, we computed the auto-correlation function of the CO2 dipole moment responsible for the absorption transition. Its Fourier-Laplace transform directly yields the spectrum. Calculations were made for two temperatures, 200 and 296 K, at 1 atm and for a large range of the Doppler widths, from the near-Doppler regime to the collision-dominant regime. For each temperature and each line, the spectra calculated for various Doppler widths were simultaneously fit with the Hartmann-Tran (HT) profile. This refined profile, which takes into account the effects of the speed dependent collisional line broadening, the Dicke narrowing and the collisional line mixing, was recommended as a reference model to be used in high-resolution spectroscopy (instead of the simplified Voigt model). The HT parameters retrieved from rCMDS-calculated spectra were then directly compared with those deduced from high-precision measurements [Wilzewski et al, JQSRT, 206, 2018, 296-305]. The results show a very good agreement, even for those parameters whose influence on the spectra is very small. Good agreement is also obtained between measured and predicted temperature dependences of these parameters. This demonstrates that rCMDS is an excellent tool, highly competitive with respect to high quality measurements for precise line-shape study