Theoretical study of the HCS+–H2 van der Waals complex: potential energy surface, rovibrational bound states, and rotationally inelastic collisional cross sections

An accurate ground-state intermolecular potential energy surface (PES) was calculated for the HCS (Formula presented.) –H (Formula presented.) complex. The surface was constructed from 3023 ab initio energies, computed with explicitly correlated coupled-cluster theory, CCSD(T)-F12b, with extrapolation to the complete basis set limit (VTZ-F12/VQZ-F12). The new 4D PES was used to compute rovibrational energies, rotational constants, and close-coupling quantum scattering calculations at low collision energies. A symmetry-adapted Lanczos algorithm was used to variationally compute the low-lying rovibrational bound states. Rotational constants for states of two isomers were determined from the energy levels and reported in hopes of motivating experiments. The rotationally inelastic state-to-state cross sections of HCS (Formula presented.) by collision with para- and ortho-H (Formula presented.) were computed and compared, and trends and propensities are discussed.