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

Abstract

An accurate ground-state intermolecular potential energy surface (PES) was calculated for the HCS${}^{+}$–H${}_2$ 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${}^{+}$ by collision with para- and ortho-H${}_2$ were computed and compared, and trends and propensities are discussed.

GRAPHICAL ABSTRACT

Keywords:

• ISM
• PES
• inelastic scattering
• rovibrational

Acknowledgments

This paper is dedicated to Professor John Stanton, whose predictions have frequently challenged or motivated experimental measurements.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

R.D. and E.Q.-S. are supported by the U.S. Department of Energy [Award DE-SC0019740]. Computing resources were supported by the National Science Foundation [Grant No. OAC-1919789].