Molecular field and spin-orbit splittings in the 2p ionization of second-row elements:: a Breit-Pauli approximation applied to OCS, SO2, and PF3

An ab initio Breit-Pauli (BP) approach is applied for 2p ionized states, P-2(3/2) and P-2(1/2) of OCS, SO2, and PF3. Diagonal elements in the BP spin-orbit Hamiltonian matrix over six 2p(-1) hole configurations are corrected by using non-relativistic 2p hole-state energies based on configuration interaction (CI) with single and double substitutions from reference states with five electrons in the 2p manifold, (2p)(3)-SDCI. The molecular field splitting in the P-2(3/2) Stale is sensitive to geometric relaxation in the core hole state, and the spin-orbit splitting is sensitive to relaxation in the 2p orbital itself. The spin-orbit wavefunction is characterized in terms of sigma and pi -type chemical bonds. (C) 2000 Elsevier Science B.V. All rights reserved.