Variable energy photoelectron spectroscopy: electronic structure and electronic relaxation

Use of variable photon energy with polarization available from synchrotron radiation has revolutionized the use of photoelectron spectroscopy (PES) in the study of transition metal complexes. The intensity dependence of PES peaks allows their definite assignment, a quantitation of the covalent mixing of the metal and ligand valence orbitals over the entire valence band, and an experimental determination of electronic relaxation. The last effect is the change in electronic structure with ionization, which is found to be large for transition metal complexes. Variable energy PES (VEPES) provides a powerful method to study bonding and its change with ionization and this provides fundamental insight into redox processes in inorganic and bioinorganic chemistry.