Collisional excitation of isotopologs of H2S by molecular hydrogen: D2S and HDS

Abstract

ABSTRACT Rate coefficients for transitions between the lower rotational levels of two isotopologs of hydrogen sulphide, specifically HDS and D2S, induced by collisions with para-H2 and ortho-H2 are presented in this work. The availability of these rate coefficients will allow accurate estimates to be made of the abundance of these species in the interstellar medium to be made from astronomical observations. The rate coefficients were computed in close-coupling calculations using potential energy surfaces (PESs) obtained by transformation of the H2S–H2 PES previously calculated with the explicitly correlated CCSD(T)-F12a coupled-cluster method. Rate coefficients for transitions between rotational levels with energies less than 196 cm−1 and temperatures from 5 to 400 K have been calculated for HDS, ortho-D2S, and para-D2S. The rate coefficients for the H2S–H2, HDS–H2, and D2S–H2 systems are compared