Global three-dimensional potential energy surfaces of H2S from the ab initio effective valence shell Hamiltonian method

The correlated, size extensive ab initio effective valence shell Hamiltonian (HV) method is used to compute three-dimensional potential energy surfaces for the ground and several excited electronic states of the H2S molecule. A single calculation of the HV simultaneously generates all states of interest as well as ionization potentials. Particular emphasis is placed on the two lowest 1 1A″ excited surfaces (one valencelike and the other Rydberg-type) that are involved in recent experiments probing nonadiabatic photodissociation processes. Supplementary effective operator calculations generate three-dimensional surfaces of dipole moments and transition dipole matrix elements, but emphasis is placed on the transition dipoles relevant to the dissociation process. Comparisons to both experiment and previous calculations for this system support the ability of multireference perturbation methods to describe global potential energy surfaces for open shell systems. We discuss the implication of our calculations for interpreting and reproducing experimental observations of the dissociation dynamics.