Vibronic and electronic states of doubly charged H₂S studied by Auger and charge transfer spectroscopy and by ab initio calculations

Doubly ionic states of H₂S are investigated by means of Auger and double charge transfer spectroscopy. From the kinetic energy distribution of H^- ions arising from double charge transfer of protons impinging on gaseous H₂S several singlet state energies of H₂S ^{2 +} have been resolved in the 30 to 50 eV energy region. The most intense experimental peak is narrow proving that the doubly ionized ground state is stable or quasi-stable. The L_II,III VV Auger electron spectrum exhibits a number of well-defined structures which exhibit vibrational fine structure in the outermost bands. The assignments of the charge transfer states and of the Auger bands are given by ab initio MCSCF electronic structure calculations. We also present vertical double ionization energies, optimized geometries and normal coordinate analysis for the neutral, single and double ionized states. A vibrational analysis of the resolved Auger bands is carried out by employing a recently derived theory for vibrational decay of short-lived core hole states in polyatomic molecules.