An ultraviolet photoelectron spectroscopic study of the H2S dimer, a van der Waals molecule

Abstract

The ultraviolet photoelectron spectrum of the H2S dimer shows four features with vertical ionization energies of 9.75, 10.95, 12.37 and 13.69 eV; the adiabatic ionization energies of the first two ionic states are 9.56 and 10.75 eV. Molecular-orbital calculations reveal that the first two features are due to the sulphur lone pairs while the others to the ∏SH2 orbitals. The ground ionic state (1 2A″) of the dimer is bound by 0.96 eV and the structure undergoes significant distortion on ionization. The first excited ionic state (1 2A′) is repulsive.