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In this paper a simple approximate approach is used to reproduce the ab initio results for the deexcitation spectral profiles of a metastable helium atom at different distances from a surface. The main quantities of our method are the spin dependent local density of states (LDOS) around the excited helium atom. We show that the extension of the spherical volumes around the atom in which we evaluate the LDOS are the only relevant parameters in this approach and they do not depend on the atom–surface distance.

Electrostatic fields of the order of 1 V/A, as they occur at field emission tips, are comparable to those experienced by valence electrons in atoms and molecules. Such fields are strong enough to induce a significant redistribution of the valence charge in chemical bonds. In this work we investigate the effects on the electronic properties of a single adatom on a metal surface induced by the presence of an electrostatic field. In particular we present the results of a full ab initio DFT calculation, within the embedding method, of the CCV Auger spectra of Si and Mg atoms in and on a jellium–Ag host. Differently from impurities in bulk, Auger spectral profiles of adsorbates on metal surfaces can show notable modifications due to the applied electric field.

In this work we investigate the deexcitation process of a slow metastable helium atom (He*) in its triplet state on simple metal surfaces. We compute the electronic properties of the interacting He*-metal (jellium-like) system, using the embedding Green's function method, within the framework of density functional theory. The Auger deexcitation rates are calculated at different distances from the surface using the Fermi golden rule, and the energy distribution of the emitted electrons is obtained by integrating the Auger rates along the classical trajectory followed by the atom in the scattering process. We present the results for three metal surfaces (Al, Na, and Cs) which are sufficiently different to span the distinct deexcitation mechanisms taking place when the He* interacts with the surface: resonant ionization + Auger neutralization for high work function substrates, and Auger deexcitation for low work function ones. Our results for the deexcitation spectral profiles are in good agreement with the experimental ones. (c) 2005 Elsevier B.V. All rights reserved.

In this letter the core-core-valence Auger transitions of an atomic impurity, both in bulk or adsorbed on a jellium-like surface, are computed within a DFT framework. The Auger rates calculated by the Fermi golden rule are compared with those determined by an approximate and simpler expression. This is based on the local density of states (LDOS) with a core hole present, in a region around the impurity nucleus. Different atoms, Na and Mg, solids, Al and Ag, and several impurity locations are considered. We obtain an excellent agreement between KL1V and KL23V rates worked out with the two approaches. The radius of the sphere in which we calculate the LDOS is the relevant parameter of the simpler approach. Its value only depends on the atomic species regardless of the location of the impurity and the type of substrate. (C) 2003 Elsevier B.V. All rights reserved.

In this work we perform a full ab initio density-functional theory calculation, within the embedding method, of the Auger spectra of atomic impurities both inside a metal bulk and just inside the solid surface and chemisorbed on it. We consider a Na atom on and in a jellium-Ag host. In particular, the Auger spectra of the electronic transitions ${\mathrm{KL}}_{1}V$ and ${\mathrm{KL}}_{2,3}V$ (core-core-valence) are worked out. The calculated profiles display features which are different for the same atom adsorbed on a metal and inside the same bulk material. Such specific features could help identifying the contribution to the measured Auger signal only due to adsorbates.

In this work we investigate the Auger deexcitation process of a slow metastable helium atom $({\mathrm{He}}^{*})$ in its triplet state on a Na surface. The electronic properties and the Auger rates of the interacting atom-metal system are calculated self-consistently at any distance of ${\mathrm{He}}^{*}$ from the surface in the framework of the local spin-density approximation using the embedding Green's function method. The energy distribution of the emitted electrons is obtained by integrating the Auger rates along the classical trajectory in the adiabatic approximation. The analysis of the spin-resolved local density of states shows that the excited atomic states broaden into resonances already at large atom-surface distances. The calculated atom deexcitation rates are in good agreement with experimental results.