Ab-initio simulation of molecular Auger spectra: nuclear dynamics effects in the spectra of carbonyl sulfide

A theoretical ab initio simulation of the carbon and oxygen KLL and sulfur LMM Auger spectra of carbonyl sulfide is presented and discussed. The underlying vertical double ionization spectrum is computed using a Green’s function method; the Auger intensity distributions are estimated via a two-hole population analysis of the eigenvectors and the main effects of nuclear vibrational motion on the energy position and broadening of the Auger bands are taken into account. The simulation yields accurate spectra, revealing the important role played by the nuclear dynamics effects at the origin of the very different shapes of the three spectra. These effects are particularly striking in the sulfur LMM spectrum, which is additionally characterized by evident spin–orbit coupling in the decaying state.