Cold collisions of SH − with He: Potential energy surface and rate coefficients

Collisional energy transfer under cold conditions is of great importance from the fundamental and applicative point of view. Here, we investigate low temperature collisions of the SH− anion with He. We have generated a three-dimensional potential energy surface (PES) for the SH−(X1Σ+)–He(1S) van der Waals complex. The ab initio multi-dimensional interaction PES was computed using the explicitly correlated coupled cluster approach with simple, double, and perturbative triple excitation in conjunction with the augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. The PES presents two minima located at linear geometries. Then, the PES was averaged over the ground vibrational wave function of the SH− molecule and the resulting two-dimensional PES was incorporated into exact quantum mechanical close coupling calculations to study the collisional excitation of SH− by He. We have computed inelastic cross sections among the 11 first rotational levels of SH− for energies up to 2500 cm−...