He + scattering from Ni, A1, and their alloy. Model calculation of the charge exchange

GARCIA E.; E. C. GOLDBERG

SURFACE SCIENCE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1996 vol. 364 p. 193 - 198

0039-6028

The changes in the He + neutralization probability when scattered from pure A1 and Ni targets and from a NiAI alloy are analyzed.The neutralization probability is calculated using a time-dependent quantum formalism which allows incorporation of severalelectronic bands of localized and extended nature in the description of the target band structure. The parameters of the interactionHamiltonian are obtained from an ab-initio model based on a pair-bonds superposition. We find that for He + scattering from A1atoms in NiAI the neutralization is less probable than for He + scattering from pure A1, while for the scattering from Ni atoms thereis no change in the neutralization probability when going from pure Ni to the alloy target. These results are in agreement with theexperimental trends which show a matrix-dependent signal only for the scattering from A1. The marked difference in the neutralizationbehavior of He + can be explained by taking into account the differences in the electronic structure between pure A! and NiAI alloy,and the presence of the corelike AI-2p state which promotes the charge exchange process at low primary He + energies.