Molecular-field splitting of the 2p(3/2) peak in x-ray photoelectron spectra of second-row atoms: A theoretical study of phosphine and phosphorus trifluoride

The theory of molecular-field-induced splitting of the 2p(3/2) peak in x-ra y photoelectron spectra of second-row atoms is reexamined, using PH3 and PF 3 as examples. Existing theory, which includes crystal field and pseudoatom ic valence effects, is found to describe correctly the electrostatic field in the 2p region, but, nevertheless, to severely underestimate the magnitud e of the resulting molecular-field splitting. Numerical simulations show th at core-valence correlation in the core ionized, final states is responsibl e for amplifying the molecular-field splitting to the extent that it is obs ervable with the present resolution. A detailed analysis based on second-or der Moller-Plesset theory is presented of these correlation effects. A qual itative model is developed which predicts that the contribution from core-v alence correlation scales with the asymmetry of the valence shell at the at om of interest. This represents an extension of the pseudoatomic valence th eory, to take into account not only electrostatic and exchange effects, but also core-valence correlation. (C) 1999 American Institute of Physics. [S0 021-9606(99)00734-5].