Ab initio study of the ground and excited states of hydrogen sulphide using SCF and CI calculations

Results from ab initio SCF and CI calculations on the ground state and low-lying valence and Rydberg states of H₂S are reported. A double ξ basis of contracted gaussian functions augmented by polarization and diffuse 3d, 4s and 4p functions is used for the calculations. The geometries of various excited states are studied by means of SCF calculations. The first observed band in the absorption spectrum is predicted to arise from the overlapping of transitions from the 2b₁ orbital to a Rydberg 4s and strongly bent valence upper state. The calculations support the assignment of other spectral features to transitions from the 2b₁ to components of the Rydberg 3d and 4p orbitals.