Line-shape parameters and their temperature dependences predicted from molecular dynamics simulations for O-2- and air-broadened CO2 lines

摘要

Requantized classical molecular dynamics simulations (rCMDS) were performed for CO2 highly diluted in O-2 at 200, 250, 296 and 350K using a site-site intermolecular potential. The simulations were made for 0.5 atm of O-2 pressure and for a large range of Doppler widths, covering near-Doppler regime to collisional-dominant regime. The Fourier-Laplace transform of the auto-correlation functions of the dipole moment, calculated by rCMDS, leads to the associated spectra of CO2 broadened by O-2. Different effects of collisions between CO2 and O-2 molecules are included in the simulated spectra. In order to determine the profile parameters of O-2-broadened CO2 lines, the rCMDS-calculated spectra were fitted with the speed-dependent Nelkin-Ghatak profile associated with the first-order line mixing. The collisional line broadening coefficient, its speed dependence component, the Dicke narrowing and the first-order line-mixing parameters were retrieved for lines with J up to 50 and for all considered temperatures. The temperature dependences of these line-shape parameters were then deduced using the usual single power law. From results obtained in this work and those obtained for CO2 in N2 [Nguyen et al., J Chem Phys, 149, 224301, 2018], the air-broadened line-shape parameters and their temperature dependences for CO2 lines were calculated and compared with literature data showing very good agreement. (C) 2019 Elsevier Ltd. All rights reserved.