Münster 1999 – scientific programme

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M: Metallphysik

M 26: Postersitzung

M 26.10: Poster

Thursday, March 25, 1999, 15:00–19:00, Aula

Neutralisation of a point charge entering a metal surface — •S. Glaubrecht, I. Tokatly, and O. Pankratov — Lehrstuhl für theoretische Festkörperphysik, Universit"at Erlangen-N"urnberg, Staudtstr.7, 91058 Erlangen

Recent experiments with the deposition of slow highly charged ions on metals open a new way to probe the dynamics of the Fermi gas. The ion projectile carries a potential energy of several hundreds of keV and the mechanism of transformation of this enormous energy into electronic excitations of the metal is yet not clear. There are several channels that contribute to this transformation: the generation of bulk and surface plasmons and the excitation of particle-hole pairs (Landau damping).
To clarify the mechanism of the energy transformation we consider the evolution of the electron density during the ion impact with the surface. We monitor the formation of the neutralisation cloud by the flow of electrons in the metal. The contributions of energy channels associated with bulk and surface plasmon generation and electron-hole pair excitations are considered separately in order to judge which one is dominant and to get the information about the dependence on the ion velocity. As a first step to describe the neutralisation process theoretically, we use a linear response method in a hydrodynamic approximation. To allow for Landau damping an additional imaginary term in the hydrodynamic response function is introduced so that the corresponding part of the RPA response function is reproduced correctly [1].

[1] R.Núñez, P.M. Echenique, R.H. Ritchie, J.Phys.C 13, 4229-46 (1980)