Chemical Shifts of Auger Electron Lines and Electron Binding Energies in Free Molecules. Silicon Compounds

The silicon KL2, 3L2, 3(1D2) Auger energies and the silicon 2p3/2 binding energies have been measured for more than twenty organic silicon compounds in the gas phase. The group shift model has been applied to the Auger energy data as well as the binding energy data. Approximate proportionality between these two types of chemical shifts was found for some sub-series of the type SiR4-nTn. The transition potential model for the transition from one to two holes in the silicon core has been developed to take into account the difference between the 1s and 2p binding energy shifts. Semi-empirical calculations have been performed for most of the compounds, CNDO/2 and EWMO (a modified iterative extended Huckel method, briefly presented in the text). It was found that EWMO provides a more satisfactory description of the valence charge densities and their changes upon core ionization than does CNDO/2. The correlation with the experimental data was also found to be better applying the transition potential models to the EWMO calculated charges than to the CNDO/2 charges.