Ab initio potential energy surfaces, bound states and electronic spectrum of the Ar-SH complex

New ab initio potential energy surfaces for the doublet pi ground electronic state of the Ar-SH complex are presented, calculated at the RCCSD(T)/aug-cc-pV5Z level. Weakly bound rotation-vibration levels are calculated using coupled-channel methods that properly account for the coupling between the two electronic states. The resulting wavefunctions are analysed and a new adiabatic approximation including spin-orbit coupling is proposed. The ground-state wavefunctions are combined with those obtained for the excited doublet sigma + state [Phys. Chem. Chem. Phys. 6, 5463 (2004)] to produce transition dipole moments. Modelling the transition intensities as a combination of these dipole moments and calculated lifetime values [J. Chem. Phys. 109, 170 (1998)] leads to a good representation of the experimental fluorescence excitation spectrum [J. Chem. Phys. 98, 4301 (1993)].