Modelling the energy-loss mechanism of charged particles in organic solids

The present study examines the energy-loss mechanism of charged particles in organic solids as determined by the inelastic interactions with the electronic sub-system of the target. The dielectric approach was applied to non-conducting valence electrons while an appropriate binary collision theory was used for core-electron transitions. The development of energy-loss models based on optical data (i.e. at zero momentum transfer) and appropriate extension algorithms (to non-zero momentum transfer) is discussed. The optical absorption spectrum is now available for a variety of organic compounds and allows for the inclusion of phase effects by incorporating pertinent experimental information. The dispersion of the optical functions is based on an analysis of the general properties of the Bethe-surface. Calculations are presented for the case of liquid water as a model substance for other condensed organic materials with very similar absorption characteristics.