Description electron binding energies

The quasiparticle approximation has succeeded in the description of valence ionization spectra of many systems. Recently, it has been shown that reliable results also can be obtained for core electron binding energies [26], In this section, we will describe some recent developments that have been realized with the quasiparticle approximation. 

Improvements in experimental technique and analysis will no doubt continue to be made with most emphasis on valence band spectra, and perhaps involving the measurement of other parameters simultaneously with ionization energies. For example, electron impact ionization experiments on gas molecules with determination of the kinematics of incident and emitted electrons can provide information on electron binding energies and on the momentum distribution of valence electrons,< > allowing a very severe test of theoretical descriptions. 

It was seen in the previous section that the main difference between Bethe s and Bohr s descriptions lies in the dynamics of close collisions, in which electron binding is unimportant. This feature is beautifully illustrated by Bethe s sum rule [5] which expresses the mean energy transfer to a target electron at a given momentum transfer hq as... 

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