Rotational excitation of sulfur monoxide in collision with helium at high temperature

LERMA and UMR 8112 of CNRS, Observatoire de Paris-Meudon, 92195 Meudon Cedex, France e-mail: francois.lique@obspm.fr

Received: 15 November 2005
Accepted: 15 December 2005

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. This will allow investigators to study in much greater detail the composition and evolution of molecules in space. Modeling of the spectra will require accurate radiative and collisional rates of species of astrophysical interest.Aims.We calculate new rates coefficients for the 91 first rotational levels of the SO molecule in collision with He for temperatures ranging from 50 to 300 K.Methods.Different levels of approximations (IOS, IOS scaling relationship) are tested in comparison with the exact full close coupling approach. From the analysis of the validity range of each method, we define a hybrid approach combining the accuracy of the full close coupling method and the less time consuming approximations (IOS, IOS scaling relationship).Results.The new rate coefficients are calculated up to 300 K. These coefficients differ significantly from previously published ones.