Singlet to triplet conversion in low energy metastable helium-metal surface collisions: Auger deexcitation process

Borisov, Andrei G.; Teillet‐Billy, D.; Gauyacq, J.P.

doi:10.1016/0039-6028(94)00742-x

Cited by 19 publications

(11 citation statements)

References 35 publications

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“…The former process, however, occurs with much higher probability because the 2s electron is much more diffuse and thus overlaps much effectively with a surface orbital. Mechanism I is supported by various theoretical calculations. − , …”

Section: Singlet−triplet Conversion Of Metastable He Atomsmentioning

confidence: 70%

“…The conversion of He*(2 1 S) to He*(2 3 S) on alkali metal surfaces has been the subject of intense experimental ,− and theoretical − studies in the past years. Roussel found for the first time the experimental evidence for the singlet−triplet conversion .…”

Section: Singlet−triplet Conversion Of Metastable He Atomsmentioning

confidence: 99%

“…Mechanism I is supported by various theoretical calculations. [104][105][106][107][108][109]112 Mechanism II: 29 The mechanism is illustrated in Figure 18. In the figure the energy positions of the occupied and affinity 2s levels of He*(2 1 S) and He*-(2 3 S) are shown as a function of atom-surface distance.…”

Section: Singlet−triplet Conversion Of Metastable He Atomsmentioning

confidence: 99%

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Electron Spectroscopy Using Metastable Atoms as Probes for Solid Surfaces

1997

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Section: Singlet−triplet Conversion Of Metastable He Atomsmentioning

confidence: 70%

Section: Singlet−triplet Conversion Of Metastable He Atomsmentioning

confidence: 99%

Section: Singlet−triplet Conversion Of Metastable He Atomsmentioning

confidence: 99%

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Electron Spectroscopy Using Metastable Atoms as Probes for Solid Surfaces

1997

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“…At this point one clearly sees that in the derivation of the levelwidths due to Auger and autodetachment processes we did not factorize out the distribution functions as it is the case in the derivation of the levelwidths due to singleelectron transfers. As a result, the distribution functions for the metal electron appear in front of the width functions in (67) and (68) but not in ( 69)- (72), where they are contained in the width functions themselves.…”

Section: Quantum Kineticsmentioning

confidence: 99%

Ion-induced secondary electron emission from metal surfaces

Pamperin

Bronold

Fehske

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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“…All these calculations assume that the helium ground state is the only one active channel in the charge exchange with the band states of the surface. Nevertheless, there are other works that have suggested that the excited states of helium could be involved in the charge exchange with a metal surface [37][38][39]. On the other hand, there are experimental evidences of electron emission in the He + /Al collision [22] that can be explained by a non-negligible population of the He excited states.…”

Section: Introductionmentioning

confidence: 99%

Importance of considering helium excited states inHe+scattering by an aluminum surface

2014

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The He + /Al system is a very interesting projectile-surface combination which was thought initially as an example of a pure Auger neutralization mechanism. Then, because of the measured reionization explained by the antibonding interaction of the projectile state with the core target states, the resonant charge exchange with the band states was considered as another important contribution to the neutralization. Nevertheless, by only considering the neutralization to the ground state of helium, the measured ion survival probability is still overestimated. On the other hand, measurements of electron emission from an Al surface bombarded by He positive ions suggested the possibility of occupied excited states of helium due to the ion-surface collision. In this work, we also include the excited states of He within the time-dependent scattering process in which both neutralization mechanisms, resonant and Auger, are simultaneously contemplated. Our starting point is a multiorbital Anderson Hamiltonian projected over the selected space of ground and excited atomic configurations. An extra term related to the Auger mechanism is added to this Hamiltonian. A difference with previous works is that this approach includes the electron spin and, therefore, the spin fluctuation statistics in the charge-exchange process is correctly taken into account. We find a notable improvement in the agreement with the experiments and also that the interference between both mechanisms is not dramatic.

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Singlet to triplet conversion in low energy metastable helium-metal surface collisions: Auger deexcitation process

Cited by 19 publications

References 35 publications

Electron Spectroscopy Using Metastable Atoms as Probes for Solid Surfaces

Electron Spectroscopy Using Metastable Atoms as Probes for Solid Surfaces

Ion-induced secondary electron emission from metal surfaces

Importance of considering helium excited states inHe+scattering by an aluminum surface

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