Electron Inelastic Mean Free Paths in Condensed Matter Down to a Few Electronvolts

A new method is reported for a simple, yet reliable, calculation of electron inelastic mean free paths in insulating and conducting materials, from the very low energies of hot electrons up to the high energies characteristic of electron beams. Through a detailed consideration of the condensed phase nature of the target, as well as the energy transferred by the projectile in individual and collective electronic excitations and the inclusion of higher order corrections to the dielectric formalism, mean free paths are calculated for water, aluminum, gold, and copper in excellent agreement with available experimental data, even at the elusive very low-energy region. These results are important because of the crucial role played by low-energy electrons in radiobiology (owing to their relevant effects in biodamage) and to elucidate the disagreement between older and recent measurements of low-energy electron mean free paths in metals (relevant for low-energy electron transport and effects in nanostructured devices) that is not yet elucidated.