Rotational relaxation of H₂S by collision with He

¹ Núcleo de Astroquímica y Astrofísica, Instituto de Ciencias Químicas Aplicadas, Facultad de Ingeniería, Universidad Autónoma de Chile, Av. Pedro de Valdivia 425, Providencia, Santiago, Chile
e-mail: otoniel.denis@uautonoma.cl
² Institut des Sciences Moléculaires, Université de Bordeaux, CNRS UMR 5255, 33405 Talence Cedex, France
e-mail: thierry.stoecklin@u-bordeaux.fr

Received: 25 February 2020
Accepted: 17 April 2020

Abstract

Context. The H₂S molecule has been detected in several regions of the interstellar medium (ISM). The use of non-LTE models requires knowledge of accurate collisional rate coefficients of the molecules detected with the most common collider in the ISM.

Aims. The main goal of this work is to study the collision of H₂S with He.

Methods. A grid of ab initio energies was computed at the coupled cluster level of theory including single, double, and perturbative triple excitations (CCSD(T)) and using the augmented correlation consistent polarized quadruple zeta (aug-cc-pVQZ) basis set supplemented by a set of mid-bond functions. These energies were fitted to an analytical function, which was employed to study the dynamics of the system. Close coupling calculations were performed to study the collision of H₂S with He.

Results. The rate coefficients determined from the close coupling calculation were compared with those of the collision with H₂O+He, and large differences were found. Finally, the rate coefficients for the lower rotational de-excitation of H₂S by collision with He are reported.