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Effects of the atomic level shift in the Auger neutralization rates of noble metal surfaces.

Monreal RC, Goebl D, Primetzhofer D, Bauer P - Nucl Instrum Methods Phys Res B (2013)

Bottom Line: In this work we compare characteristics of Auger neutralization of [Formula: see text] ions at noble metal and free-electron metal surfaces.For noble metals, we find that the position of the energy level of He with respect to the Fermi level has a non-negligible influence on the values of the calculated Auger rates through the evaluation of the surface dielectric susceptibility.We conclude that even though our calculated rates are accurate, further theoretical effort is needed to obtain realistic values of the energy level of He in front of these surfaces.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Centre (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain.

ABSTRACT

In this work we compare characteristics of Auger neutralization of [Formula: see text] ions at noble metal and free-electron metal surfaces. For noble metals, we find that the position of the energy level of He with respect to the Fermi level has a non-negligible influence on the values of the calculated Auger rates through the evaluation of the surface dielectric susceptibility. We conclude that even though our calculated rates are accurate, further theoretical effort is needed to obtain realistic values of the energy level of He in front of these surfaces.

No MeSH data available.


Schematic energy diagram for interaction of He with a high work function metal surface. W: work function; blue shaded area: occupied states of conduction band; brown curves: energy levels of He as function of distance from the surface for states indicated. Green arrow: resonant neutralization (RN), blue arrows: Auger neutralization (AN). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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f0005: Schematic energy diagram for interaction of He with a high work function metal surface. W: work function; blue shaded area: occupied states of conduction band; brown curves: energy levels of He as function of distance from the surface for states indicated. Green arrow: resonant neutralization (RN), blue arrows: Auger neutralization (AN). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Mentions: Besides resonant tunneling, Auger processes are the second fundamental electron transfer processes for ion–surface interactions. Auger neutralization (AN) and Auger ionization (AI) are two-electron processes. In AN, one electron from the surface is transferred to a bound state (often the ground state) of the atom while, by virtue of electron–electron interaction, energy and momentum are transferred to the solid creating surface excitations (electron–hole pairs and plasmons). In AI an electron bound to the atom is transferred to a state above the Fermi energy with the creation of surface excitations. Energy conservation requires kinetic energy from the atom and therefore AI is only possible above a threshold kinetic energy. Being two-electron processes, Auger processes are generally less efficient than resonant charge transfer and can be best studied in situations where the latter are energetically forbidden. In this work we will be concerned with systems in which slow noble gas ions are incident on high work function metal surfaces. For these systems the atomic ground state is non-degenerate with the occupied electronic states of the surface and the atomic excited states are resonant with the empty states of the metal. Fig. 1 illustrates schematically the relative positions of the different energy levels for the case of . Moreover, since the ion velocity is typically much smaller that the Fermi velocity of the metal electrons, AI processes are not possible. Therefore, these are ideal systems to isolate and study Auger neutralization since it is the only possible mechanism of charge transfer.


Effects of the atomic level shift in the Auger neutralization rates of noble metal surfaces.

Monreal RC, Goebl D, Primetzhofer D, Bauer P - Nucl Instrum Methods Phys Res B (2013)

Schematic energy diagram for interaction of He with a high work function metal surface. W: work function; blue shaded area: occupied states of conduction band; brown curves: energy levels of He as function of distance from the surface for states indicated. Green arrow: resonant neutralization (RN), blue arrows: Auger neutralization (AN). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4376069&req=5

f0005: Schematic energy diagram for interaction of He with a high work function metal surface. W: work function; blue shaded area: occupied states of conduction band; brown curves: energy levels of He as function of distance from the surface for states indicated. Green arrow: resonant neutralization (RN), blue arrows: Auger neutralization (AN). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Mentions: Besides resonant tunneling, Auger processes are the second fundamental electron transfer processes for ion–surface interactions. Auger neutralization (AN) and Auger ionization (AI) are two-electron processes. In AN, one electron from the surface is transferred to a bound state (often the ground state) of the atom while, by virtue of electron–electron interaction, energy and momentum are transferred to the solid creating surface excitations (electron–hole pairs and plasmons). In AI an electron bound to the atom is transferred to a state above the Fermi energy with the creation of surface excitations. Energy conservation requires kinetic energy from the atom and therefore AI is only possible above a threshold kinetic energy. Being two-electron processes, Auger processes are generally less efficient than resonant charge transfer and can be best studied in situations where the latter are energetically forbidden. In this work we will be concerned with systems in which slow noble gas ions are incident on high work function metal surfaces. For these systems the atomic ground state is non-degenerate with the occupied electronic states of the surface and the atomic excited states are resonant with the empty states of the metal. Fig. 1 illustrates schematically the relative positions of the different energy levels for the case of . Moreover, since the ion velocity is typically much smaller that the Fermi velocity of the metal electrons, AI processes are not possible. Therefore, these are ideal systems to isolate and study Auger neutralization since it is the only possible mechanism of charge transfer.

Bottom Line: In this work we compare characteristics of Auger neutralization of [Formula: see text] ions at noble metal and free-electron metal surfaces.For noble metals, we find that the position of the energy level of He with respect to the Fermi level has a non-negligible influence on the values of the calculated Auger rates through the evaluation of the surface dielectric susceptibility.We conclude that even though our calculated rates are accurate, further theoretical effort is needed to obtain realistic values of the energy level of He in front of these surfaces.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Centre (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain.

ABSTRACT

In this work we compare characteristics of Auger neutralization of [Formula: see text] ions at noble metal and free-electron metal surfaces. For noble metals, we find that the position of the energy level of He with respect to the Fermi level has a non-negligible influence on the values of the calculated Auger rates through the evaluation of the surface dielectric susceptibility. We conclude that even though our calculated rates are accurate, further theoretical effort is needed to obtain realistic values of the energy level of He in front of these surfaces.

No MeSH data available.