Linear combination of atomic orbitals calculation of the Auger neutralization rate ofHe+on Al(111), (100), and (110) surfaces

Abstract

We develop a theory of the Auger neutralization rate of ions on solid surfaces in which the matrix elements for the transition are calculated by means of a linear combination of atomic orbitals technique. We apply the theory to the calculation of the Auger rate of He + on unreconstructed Al͑111͒, ͑100͒, and ͑110͒ surfaces, assuming He + to approach these surfaces on high symmetry positions and compare them with the results of the jellium model. Although there are substantial differences between the Auger rates calculated with both kinds of approaches, those differences tend to compensate when evaluating the integral along the ion trajectory and, consequently, are of minor influence in some physical magnitudes like the ion survival probability for perpendicular energies larger than 100 eV. We find that many atoms contribute to the Auger process and small effects of lateral corrugation are registered.

Band structure effects in Auger neutralization of He ions at metal surfaces

“…To this end, a theory of AN was formulated using a Linear Combination of Atomic Orbitals (LCAO) basis for the metal electrons. 21 This model successfully explains experimental results for the neutralization of He ions at Al and Ag surfaces in the grazing scattering regime. [22][23][24] Recent experiments for He + ions scattered from Cu and Au crystals in the AN regime of LEIS exhibited a pronounced dependence of the neutralization probability on the surface orientation, similarly as discussed above for grazing collisions.…”

“…This behavior is in strong contrast to the behavior found for Al surfaces. 21 Here, the contributions originating from the nearest neighbors are larger than the contributions from the on-top atom at all distances investigated.…”

“…A theory to calculate for ions in front of metal surfaces was developed, taking into account the crystal structure of the surface. [21][22][23] Here, only the main features of this theory will be summarized. The basic idea is to separate the metal electron which neutralizes the ion from the metallic excitations taking the excess of potential energy.…”

Auger neutralization and ionization processes for charge exchange between slow noble gas atoms and solid surfaces

“…The present formulation for the corrugated Auger neutralization rate is first compared with the jellium model for He + on Al [138]. The calculation includes the 1s orbital of He and all orbitals of Al.…”

LEIS: A reliable tool for surface composition analysis?

“…3). In order to understand this crystal effect in the neutralization efficiency we theoretically limited the area where AN can take place to distances smaller than half an interlayer distance [18], [ 19 ] and assumed a homogeneous electron distribution. We calculated the time spent within this free electron gas using the MD simulation package KALYPSO [ 20 ].…”