Many Body Theory of Charge Transfer in Hyperthermal Atomic Scattering

TL;DR

This paper develops a detailed many-body theoretical model for charge transfer during hyperthermal alkali atom scattering on metallic surfaces, extending previous models to include additional physical processes and comparing results with experimental data.

Contribution

It extends the Newns-Anderson Hamiltonian approach by incorporating level crossings, excited neutrals, and negative ions, providing a more comprehensive description of charge transfer phenomena.

Findings

Neutralization probability of Na+ ions shows a minimum at intermediate velocity.

The model's predictions agree quantitatively with experimental data for alkali ions on Cu(001).

Velocity and work-function dependence of charge states are accurately captured.

Abstract

We use the Newns-Anderson Hamiltonian to describe many-body electronic processes that occur when hyperthermal alkali atoms scatter off metallic surfaces. Following Brako and Newns, we expand the electronic many-body wavefunction in the number of particle-hole pairs (we keep terms up to and including a single particle-hole pair). We extend their earlier work by including level crossings, excited neutrals and negative ions. The full set of equations of motion are integrated numerically, without further approximations, to obtain the many-body amplitudes as a function of time. The velocity and work-function dependence of final state quantities such as the distribution of ion charges and excited atomic occupancies are compared with experiment. In particular, experiments that scatter alkali ions off clean Cu(001) surfaces in the energy range 5 to 1600 eV constrain the theory quantitatively. The neutralization probability of Na$^+$ ions shows a minimum at intermediate velocity in agreement with the theory. This behavior contrasts with that of K$^+$, which shows ... (7 figures, not included. Figure requests: jbm@yollabolly.physics.brown.edu)