aDepartment of Chemistry, McMaster
University, Hamilton, ON, Canada L8S 4M1
bDepartment of Chemistry, University
of Alberta, Edmonton, AB, Canada T6G 2G2
cInstitute for Molecular Science,
Okazaki 444-8585, Japan
Abstract
Total ion yield spectra of PF3, PCl3, PCl2CF3,
OPF3 and SPF3 were recorded in the region of P 2p,
P 2s, S 2p, S 2s and halogen (Cl 2p, F 1s) excitation using synchrotron
radiation. The P 2p spectra are interpreted with GSCF3 ab initio configuration
interaction calculations optimized for core excitation studies. The experimental
- theoretical comparison is based on both absolute intensities (oscillator
strengths) and transition energies. The calculations indicate that several
of the discrete states (e.g., that in PF3 at 136.5 eV) are best
described as LS-coupled states because the core–valence electron exchange
is very large and thus the singlet–triplet splitting is larger than the
spin–orbit splitting. While the state at 136.5 eV in PF3
is particularly notable, analogous P 2p excited states with large singlet–triplet
splittings are calculated in PCl3, PCl2CF3,
OPF3 and SPF3. Aspects of partial ion
yield measurements (particularly the PF3+ yield of
PF3 and the SPF3+ yield of SPF3)
support this interpretation by revealing isolated single states without
a corresponding partner at the spin-orbit splitting. The partial ion yields
help clarify spectral interpretation by removing interference from overlap
with adjacent states having the normal (j,j)-coupled ion core character.
Published in Chemical Physics 238 (1998) 201–220.
Total ion yield (TIY) spectra of PF3, PCl3 and
PCl2CF3 in the region of the P 2p edge. The hatched
lines indicate the P 2p ionisation thresholds reported in the literature.
The spectra are characterised by peaks at low photon energy corresponding
to excitation of P 2p electrons to unoccupied valence orbitals, followed
by sharper spectral features just below the ionisation thresholds attributed
to excitation to Rydberg orbitals and broad shape resonances in the P 2p-1
ionisation continuum.
