The simplest way to calculate the energy loss of electrons during
scattering processes in solids is the formula of Bethe's stopping
power, in which the contribution of all possible excitation processes
to the energy loss has been represented by a factor called the mean
ionization energy. Representing all inelastic processes by one
stopping power, the total energy loss of an electron for
the path length S between two elastic scatterings is presented by:
with
An extension of the Bethe formula for energies less than the mean ionization energy J was published by Rao-Sahib and Wittry [RSW74]:
for energies less than .
The mean ionization potential implemented in SESAME is that from Zeller (1967 unpublished) which also has been used by Pouchou and Pichoir in the STRATA program:
The main disadvantage of the Bethe approach in Monte Carlo calculations is, that it is impossible to simulate excitation processes and the generation of secondary electrons.