title: Interaction of ions and ion clusters with a disordered electron gas: collective and single-particle excitations.
abstract: In this paper, we report results on our theoretical studies of stopping power contributions from single-particle and plasmon excitations. We have introduced an equipartition ratio defined as the ratio of stopping contributions from plasmon and single-particle excitations, respectively. Within the linear response theory we have made a comprehensive investigation of this equipartition ratio for fast pointlike and extended projectile ions in a disordered electron gas; the latter is modeled by a degenerate electron gas of metallic densities and with disorder being incorporated within a relaxation-time approximation. As simple but useful examples of pointlike and extended projectiles we have considered proton and He+ ion, as well as diproton and He+ ion clusters. We present detailed and comparative results for the equipartition ratio corresponding to several values of the damping parameter which characterizes disorder in our model. The results are also compared, wherever applicable, with those for individual, i.e., uncorrelated projectiles.
authors.affiliation: Institut für Theoretische Physik II, Universität Erlangen, Germany. hrachya@irphe.am
authors.forename: Hrachya B
authors.initials: HB
authors.lastname: Nersisyan
authors.forename: Amal K
authors.initials: AK
authors.lastname: Das
authors.forename: Hrant H
authors.initials: HH
authors.lastname: Matevosyan