Breakdown of the molecular orbital picture of ionization for inner valence electrons: experimental and theoretical study of H₂S and PH₃

The spectral function for ionization of the valence electrons of H₂S and PH₃ is computed by a many-body Green's function method. For ionization out of the 4a₁ inner valence orbital the spectral intensity is found to be distributed over numerous lines, in sharp contrast to the ionization out of the outer valence orbitals, where more than 90% of the intensity appears in the main line and less than 10% is lost to satellite lines. He(II) photoelectron spectra of the inner valence region, confirming the main features of the theoretical results, are presented. Comparison is also made with recent e-2e coincidence spectra of H₂S and PH₃.