Ro-vibrational excitation of CS by He

Abstract

Context. Over the next few years, ALMA and Herschel missions will perform high spatial and spectral resolution studies at infrared and sub-millimeter wavelengths. Modeling of the spectra will require accurate radiative and collisional rates for species of astrophysical interest. Aims. The present paper focuses on the calculation of ro-vibrational excitation rate coefficients of CS by He, useful for studies of high-temperature interstellar environments. Methods. A new accurate three dimensional (3D) potential energy surface for the CS-He system, which explicitly takes into account the r-dependence of the CS vibration, was calculated. The dynamic calculations were performed using the VCC-IOS approximation. Results. Cross sections among the 38 first rotational levels of ν - 0, ν = 1 and ν = 2 are calculated for total energies up to 10 000 cm-1. Rate coefficients between the ro-vibrational levels are calculated for temperatures from 300 K to 1500 K. © ESO 2007.