Elastic electron reflection for determination of the inelastic mean free path of medium energy electrons in 24 elemental solids for energies between 50 and 3400 TeV

The charge transfer core-hole screening depends on the ratio between the charge transfer rate and the rate of change in separation-energies between the acceptor and donor levels in a charge transfer system. The latter is related to how fast a photoelectron leaves the system. As examples we discussed the core-level XPS spectra of the N2 molecule physisorbed on graphite and the L23 XPS spectra of the formally pure divalent Cu compounds such as CuO and YBa2 Cu3 O7-delta. The interplay between the adiabatic transition and the non-adiabatic transition upon a core-electron ionization (excitation) in a charge transfer system is discussed in the light of the relaxation and core-hole decay.