Auger Electron Spectra of Molecules: The First Row Hydrides

Abstract

A semi-empirical molecular orbital approach primarily developed to predict the Auger energies and transition rates associated with complex polyatomic molecules has been evaluated by reference to the first row hydrides. For this suite of molecules, spanning a range of symmetry classes, high resolution experimental spectra and ab initio energy calculations are available for comparison. The method proposed provides a good first estimate for transition rates. Relative Auger energies are less satisfactory, especially when electron correlation effects are strong. Absolute kinetic energies are too low, principally due to the neglect of electronic relaxation. The usefulness of the approach is mainly for the interpretation of spectra for larger systems where ab initio calculations are not readily accomplished. A need for further experimental measurements obtained using photoelectron-Auger electron coincidence studies is identified to remove uncertainties associated with the extent of satellite contributions present in all the spectral profiles so far recorded. In the present work the satellite contribution to the methane Auger spectrum is estimated to be 16% of the total intensity compared with an earlier estimate in the literature of 49%.