Experimental and theoretical CO2–He pressure broadening cross sections

Abstract

We present experimental and theoretical results for the CO₂–He pressure broadening coefficients. Linewidths have been measured for the ν₃ bands of CO₂ in helium baths from 123 to 760 K with a Fourier transform interferometer. Close coupling calculations were performed with the MOLCOL program and with the most recent available potential energy surface (PES) of Negri et al. (J. Chem. Phys., 1999, 111, 6439). Generalised pressure broadening cross sections were then deduced and averaged over Maxwell–Boltzmann kinetic energy distributions to provide the thermally averaged linewidths. Theoretical calculations are in rather good agreement with the experimental data. In addition, we examine the effect of the radiation–matter interaction tensor order on the linewidths. Total inelastic cross sections obtained with the empirical PES of Beneventi et al. (J. Chem. Phys., 1988, 89, 4671) and with the ab initio PES of Yan et al. (J. Chem. Phys., 1998, 109, 10284) are also compared to those obtained with the ab initio PES of Negri et al.