Collision-induced rotational excitation of SiH + by He atom at low temperatures

Abstract

Using the Coupled Cluster with Single and Double and Perturbative Triple excitations method and the aug-cc-pVQZ basis set, we have computed a two-dimensional potential energy surface for the van der Waals complex SiH +( X 1Σ +) + He( 1S). Bond functions were placed at mid-distance between the center of mass of SiH + and He atom for a better description of the intersystem correlation interaction energy. The potential energy surface presents a global minimum of ∼308 cm −1 below the SiH +–He dissociation limit. By fitting the potential energy surface on a basis of Legendre polynomials functions, we have derived collisional excitation cross sections for the SiH + collisions with He in the Close Coupling approach. Downward rate coefficients are inferred at low temperature by averaging the cross sections over a Maxwell-Boltzmann velocity distribution. A propensity towards Δ J even parity transitions is observed in almost the entire range of energy spanned. It is expected that the data worked out in this study may enhanced further astrophysical investigations as well as laboratory experiments.