Theoretical investigations of the SH+ and LiS+ cations

Abstract Reliable theoretical data on spectroscopy and spin–orbit matrix elements are computed for the lowest electronic states of SH + and LiS + ions. Accurate spectroscopic predictions for their excited electronic states are given. For SH + , polarization minima at large internuclear distances are located in addition to the strongly bound electronic states already known. For LiS + , our calculations confirm that the electronic ground state of this ion is of 3 Σ − species and reveal the existence of a 1 Δ state presenting a potential well as deep as the potential of the ground state. Moreover, the LiS + electronic excited states potential energy curves possess shallow potential minima in the molecular region and at long-internuclear distances. Generally, these shallow minima may be populated during low energy collisions between the corresponding atomic fragments. Finally, spin–orbit calculations have allowed giving accurate determinations of the spin–orbit splittings for these cations and elucidation of the predissociation mechanisms of SH + leading to the formation of the S + and H species in their electronic ground states. Accordingly, long-lived SH + ions can be found in the X 3 Σ − , a 1 Δ and b 1 Σ + electronic states and the rovibrational levels of LiS + in its electronically excited and ground states should be weakly perturbed.