Vibrational relaxation rate coefficients in CS-He collisions up to the dissociation limit: mixed quantum-classical calculations and neural network predictions

Abstract

Rate coefficients for the process CS(v) + He → CS(v - Δv) + He with Δv=1,2,3 and for v up to 45 were calculated in the 80 K - 5000 K temperature using a mixed quantum-classical (MQC) method. The dataset was then completed using a Neural Network (NN) model, trained on the MQC rate coefficients. The reliability of the MQC method was first verified by comparing the new MQC results with initially state-selected ro-vibrational rate coefficients up to v=2 computed with the vibrational close-coupling infinite-order sudden (VCC-IOS) method [Lique & Spielfiedel Astronomy & Astrophysics, 2007, 462, 1179] employing the same potential energy surface (PES). To enable calculations for higher vibrationally excited states, a new analytical PES was developed that is suitable even under large bond distortions.