Rotational excitation of carbon monosulfide by collisions with helium

¹ LERMA and UMR 8112 of CNRS, Observatoire de Paris-Meudon, 92195 Meudon Cedex, France e-mail: francois.lique@obspm.fr
² DAMIR. IEM-CSIC, c/ Serrano 121 28006 Madrid, Spain

Received: 17 October 2005
Accepted: 15 January 2006

Abstract

Context.Over the next few years, Alma and Herschel missions will open the universe to high spatial and spectral resolution studies at infrared and sub-millimeter wavelengths. Modeling of the observed spectra will require accurate radiative and collisional rates on species of astrophysical interest.

Aims.The present paper focuses on the calculation of new rate coefficients among the 31 first rotational levels of the CS molecule in collision with He for temperatures ranging from 10 K to 300 K.

Methods.A new 2D potential energy surface for the CS-He system, calculated at a CS r-distance frozen at its experimental equilibrium distance was obtained with accurate quantum chemistry methods. Quantum close-coupling calculations lead to collisional cross sections and rate coefficients.

Results.The new rate coefficients are calculated up to 300 K. These new coefficients differ significantly from previously published ones. The consequences for astrophysical models are evaluated.