Doubly Differential Electron Yields from Thin Copper Foils Induced by Fast Ion Impact

摘要

The double-differential yields of electrons ejected from thin metal foils can provide detailed information onthe transport properties of secondary electrons produced within condensed phase material by fast charged particles.Models of charged-particle track structure in condensed phase material depend on theoretical elastic and inelasticscattering cross sections based on material parameters. Because of the uncertainties in theoretical methods used todescribe low-energy electron scattering in condensed matter and the infeasibility of direct measurements of crosssections in the condensed phase, electron transport models are tested by comparison of calculated and measured spectraof electrons that have undergone transport through the bulk and exited through the surface. Since energy and angularresolved electron yields provide the most stringent tests of theory, and electron scattering cross sections are mostuncertain for low energies, we have applied time-of-flight methods to focus on the low-energy electrons emitted fromthin (1 1.1m) copper foils produced by the transmission of 2- and 6-MeV protons and 1-MeV/u fluorine ions. Electronemission spectra for electron energies from 1 eV to several keV and emission angles from 15 to 155 degrees arepresented. Although residual electric and magnetic fields are observed to affect spectra for electron energies less thanabout one electron volt, the data provide detailed information on low-energy electron transport in a region where elasticand inelastic electron scattering cross sections are most uncertain.