On the interpretation of ion neutralisation spectra at metal surfaces

Modinos, A.; Easa, S. I.

doi:10.1016/s0039-6028(87)80178-4

“…Although the principles of secondary electron emission are known, it is still a great challenge to measure or to calculate secondary electron emission spectra, even for freestanding surfaces not in contact with a plasma. Experimentally, it requires sophisticated instrumentation [16,[29][30][31][32][33][34][35][36][37][38], whereas theoretically, the challenge is to find an efficient way to deal with a many-body scattering problem giving rise to a great variety of collision pathways [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. It is thus not surprising that the data base for secondary electron emission is rather sparse, especially for materials used as walls in laboratory gas discharges.…”

Section: Introductionmentioning

confidence: 99%

Ion-induced secondary electron emission from metal surfaces

Pamperin

¹

,

Bronold

²

,

Fehske

³

2018

Plasma Sources Sci. Technol.

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Using a helium ion hitting various metal surfaces as a model system, we describe a general quantum-kinetic approach for calculating ion-induced secondary electron emission spectra at impact energies where the emission is driven by the internal potential energy of the ion. It is based on an effective model of the Anderson-Newns-type for the subset of electronic states of the ion-surface system most strongly affected by the collision. Central to our approach is a pseudo-particle representation for the electronic configurations of the projectile which enables us, by combining it with two additional auxiliary bosons, to describe in a single Hamiltonian emission channels involving electronic configurations with different internal potential energies. It is thus possible to treat Auger neutralization of the ion on an equal footing with Auger de-excitation of temporarily formed radicals and/or negative ions. From the Dyson equations for the projectile propagators and an approximate evaluation of the selfenergies rate equations are obtained for the probabilities with which the projectile configurations occur and an electron is emitted in the course of the collision. Encouraging numerical results, especially for the helium-tungsten system, indicate the potential of our approach.

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“…Following Appelbaum and Hamman [66], Modinos and Easa [67] calculated electron spectra assuming that one of the two-electrons was localized near the ion while the second one was emitted from the surface. However, other works [68] parametrized the density of states and assumed an Auger interaction to be fully local in the sense that the wave functions of both electrons are sensitive to the spatial region around the ion.…”

Section: Theoretical Modelsmentioning

confidence: 99%

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

Monreal

¹

2014

Progress in Surface Science

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Electron and energy transfer processes between an atom or molecule and a surface are extremely important for many applications in physics and chemistry. Therefore a profound understanding of these processes is essential in order to analyze a large variety of physical systems. The microscopic description of the two-electron Auger processes, leading to neutralization/ionization of an ion/neutral atom in front of a solid surface, has been a long-standing problem. It can be dated back to the 1950s when H. D. Hagstrum proposed to use the information contained in the spectrum of the electrons emitted during the neutralization of slow noble gas ions as a surface analytical tool complementing photoelectron spectroscopy. However, only recently a comprehensive description of the Auger neutralization mechanism has been achieved by the combined efforts of theoretical and experimental methods. In this article we review the theoretical models for this problem, stressing how their outcome compare with experimental results. We also analyze the inverse problem of Auger ionization. We emphasize the understanding of the key quantities governing the processes and outline the challenges remaining. This opens new perspectives for future developments of theoretical and experimental work in this field.

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“…Many works concentrated on the calculations of the spectrum of the electrons emitted in the neutralization process in order to ascertain to which extent they carry information on the surface electronic structure. Following Appelbaum and Hamman [66], Modinos and Easa [67] calculated electron spectra assuming that one of the two-electrons was localized near the ion while the second one was emitted from the surface. However, other works [68] parametrized the density of states and assumed an Auger interaction to be fully local in the sense that the wave functions of both electrons are sensitive to the spatial region around the ion.…”

Section: Theoretical Modelsmentioning

confidence: 99%

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

Monreal

2014

Preprint

0

View full text Add to dashboard Cite

Electron and energy transfer processes between an atom or molecule and a surface are extremely important for many applications in physics and chemistry. Therefore a profound understanding of these processes is essential in order to analyze a large variety of physical systems. The microscopic description of the two-electron Auger processes, leading to neutralization/ionization of an ion/neutral atom in front of a solid surface, has been a long-standing problem. It can be dated back to the 1950s when H. D. Hagstrum proposed to use the information contained in the spectrum of the electrons emitted during the neutralization of slow noble gas ions as a surface analytical tool complementing photoelectron spectroscopy. However, only recently a comprehensive description of the Auger neutralization mechanism has been achieved by the combined efforts of theoretical and experimental methods. In this article we review the theoretical models for this problem, stressing how their outcome compare with experimental results. We also analyze the inverse problem of Auger ionization. We emphasize the understanding of the key quantities governing the processes and outline the challenges remaining. This opens new perspectives for future developments of theoretical and experimental work in this field.

show abstract

On the interpretation of ion neutralisation spectra at metal surfaces

Cited by 18 publications

References 11 publications

Ion-induced secondary electron emission from metal surfaces

Ion-induced secondary electron emission from metal surfaces

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

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

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