Solid state effects in binary-encounter electron emission from collisions with C, Al, Cu and Au foils

Abstract

We have studied binary-encounter electron ejection from thin solid foils (C, Al, Cu, Au) with highly charged swift heavy Ar 17+ ions at 13.6 MeV u −1 both experimentally and theoretically. The theory, based on the electron impact approximation describes the shape and the angular dependence well for very thin targets only (for example C less than 260 Å). For thicker targets, solid state effects (in particular, electron transport) influence the shape of the binary-encounter electron peak initially given by the target atom Compton profile. Such effects have to be taken into account in atomic collision experiments even if single-collision conditions for the primary interaction (e.g. ionization) are fulfilled. Not only may the electronic structure be different for free atoms and atoms bound in solids, but also the observable spectra of, for example, electrons may be different from the primary ones due to transport effects in condensed matter.

Fast Electron Production at Intermediate Energies: Evidence for Fermi Shuttle Acceleration and for Deviations from Simple Relativistic Kinematics

“…2. Although a very slight decrease of the velocity may be observed with increasing carbon target thickness (probably to be explained by transport effects [8]), we obtain a value around 15.5 6 0.5 cm͞ns, independent from the target atomic numbers. This value is below the value predicted by either the classic (18 cm͞ns) or relativistic (16.5 cm͞ns) two-body elastic collision kinematics.…”

Theory and measurement of absolute doubly differential cross sections of binary encounter electron ejection in collisions of swift heavy ions with solids

“…One would expect such a law from a simple two-body Rutherford scattering between a free target electron and the projectile nucleus including relativistic kinematics but a nonrelativistic Rutherford scattering formula as proposed by DePaola et al (1995). At larger angles, the EIA curve is 'flatter', as already observed and discussed by Rothard et al (1998), due to deviations from simple two-particle dynamics.…”

“…The experiments with Ar 18+ (13.6 MeV u −1 ) were performed at GANIL in Caen (France). For this collision system, relative (not absolute) cross sections for perpendicular ion impact were measured by means of a magnetic spectrometer (Rothard et al 1998).…”

“…In figure 2, comparison is also made with results from previous experiments (Rothard et al 1998), which were normalized to the EIA theory in the BE peak maximum for the thinnest target (Jakubaßa-Amundsen and Rothard 1999). Particularly at the larger target thickness (figure 2(b)) the straggling-EIA improves on the solid-EIA theory as far as the peak shape is concerned.…”