ENERGY TRANSFER, TRAPPING, AND THE INTERACTION POTENTIAL IN HYPERTHERMAL NA+ SCATTERING FROM CU(001)

摘要

In this paper we present measured energy and angular distributions for Naf scattering from Cu(001) with incident energies ranging from 10 to 100 eV. Excellent agreement with the measured spectra over the full range of incident energies is achieved with simulations using a scattering potential that consists of two parts, both of which we discuss in detail in this paper. The first is a sum of Hartree-Fock (Na-Cu)(+) pair potentials where the sum runs over the surface atoms nearest the scattering ion. To this we add an attractive potential that approaches the classical image potential fat from the surface, but saturates close to the surface. From these spectra we extract detailed information about the scattering dynamics, such as the scattering trajectories, energy transfer to the surface, and particle trapping. For energies below 100 eV we find that the scattering is particularly sensitive to the attractive term in the potential. In particular, as the incident energy is reduced the scattered angular distributions broaden, the fractional energy transfer to the surface increases, and trapping of the ions by the surface is observed. This sensitivity enables us to put bounds on the depth of the attractive well in the potential. According to the simulations there is a minimum in the trapping probability at incident energies between 15 and 30 eV. Furthermore, they indicate that the trajectories that lead to trapping at energies below and above the minimum differ markedly, particularly in the energy transfer in the initial collision with the surface. [References: 62]