Photoionization cross-sections: a guide to electronic structure

The article is concerned with photoelectron (PE) spectroscopy of transition metal molecules. The use of synchrotron radiation to measure the change in intensity of photoelectron bands with photon energy, and the presentation of these results in terms of photoionization cross-sections and branching ratios are described. The qualitative interpretation of PE cross-sections is outlined and illustrated with data from metallocenes and tetrahedral molecules. The successes and failures of the Gelius model are discussed. Methods of calculating ionization energies are presented and evaluated. Calculation of photoionization cross-sections is shown to provide a good account of many of the experimental features. Overall, the measurement and interpretation of PE data gives support to modern theoretical methods of describing the electronic structure of transition metal molecules.