VARIABLE-PHOTON-ENERGY PHOTOELECTRON SPECTROSCOPIC STUDIES OF HIGH-SPIN-D6 TETRAHEDRAL FECL-4(2-) - ELECTRONIC RELAXATION EFFECTS ON IONIZATION

Variable-photon-energy photoelectron spectra (PES) are reported for the valence band region of ferrous chloride over the energy range 25-150 eV. Changes in peak intensity as a function of photon energy are compared to atomic photoionization cross sections, allowing experimental assignment and quantitation of the PES features. These results indicate that the ground-state-bonding description in ferrous chloride corresponds to the normal description for transition-metal complexes, with the highest occupied levels containing mostly metal character, but with significant spin-polarization effects. The relatively large exchange splitting in d6splits the d levels into spin-up and spin-down sets, with the majority spin-up levels showing greater covalent mixing in both the experimental data and in spin-unrestricted SCF-Xα-SW calculations. The PE spectra further show satellite peaks with significant off-resonance intensity (~6% of the main-band intensity), indicating that a large electronic relaxation occurs upon ionization. PE spectra taken at the Fe 3p absorption edge show dominant resonance enhancement in the deeper binding-energy region of the main band as well as in the satellites. The Xα-SW calculations reproduce both the large relaxation effects and the observed resonance behavior and assign the satellites as arising from ligand ionization plus ligand-to-metal charge-transfer shakeup. © 1990, American Chemical Society. All rights reserved.