Advances in the theoretical simulation of Auger spectra of polyatomic molecules: an example

We review an efficient approach for the theoretical ab initio simulation of Augerspectra of polyatomic molecules, and discuss the results of an application to the acetaldehyde molecule. The underlying vertical double ionization spectrum, comprising hundreds of relevant transitions, is computed using a Green's function method and the extremely dense Auger intensity distributions are estimated via a two-hole population analysis of the eigenstates. The simulation incorporates the main effects of nuclear vibrational motion on the energy position and broadening of the Auger bands. This analysis is shown to be indispensable for the faithful reproduction of the very different carbon and oxygen spectral profiles and their conclusive interpretation. The experimentally unique carbon spectrum is discussed in terms of its superimposed methylic and carbonylic components.