Valence-hole localization in core-valence doubly ionized states of ionic molecules and its impact on KLV Auger spectroscopy

The complete spectra of core-valence dicationic states, i.e., states with one vacancy in the core and one in the valence shell, of the molecules BF3 , AlF3 , BCl3, and AlCl3, are investigated by the Green’s-function method. An analysis of the double-hole density in the corresponding correlated states shows that when the core hole is on a ligand ~halogen! atom, the valence hole is also strongly localized, either on the same ligand or on a different ligand. As a result these states can be classified as either on-core or off-core site states. We discuss how the localization phenomena are at the origin of the chlorine KLV Auger spectra of BCl3 and AlCl3 and, in particular, how they provide a complete and conclusive interpretation of these spectra. Due to the intraatomic nature of the Auger process, the simulation of the chlorine and aluminum KLV Auger spectra is done by a simple convolution of the respective on-core site component of the computed two-hole density distribution. The ligand atom spectra contain almost no information about the molecular system, representing an indistinct self-image of the ligand atom itself, whereas the central atom spectra render a distinct foreign image of the molecular environment. @S1050-2947~99!07009-2#