Mixed-valence correlations in charge-transferring atom–surface collisions

Pamperin, M.; Bronold, F. X.; Fehske, Holger

doi:10.1088/0031-8949/2015/t165/014008

Cited by 6 publications

(26 citation statements)

References 44 publications

(75 reference statements)

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“…The neutral fraction found in Refs. [6,7] failed in reproducing both the neutral fraction temperature dependence and neutral fractions measured. On the other hand, the neutral fractions of 1-keV incoming Mg ions calculated in [7] satisfactorily reproduce the experimental results.…”

Section: Introductionmentioning

confidence: 95%

“…The importance of working with the Green functions ( 5) and ( 6) instead of Green function (8) resides in that the latter does not permit us to easily discriminate the single and double occupation probabilities [Eqs. (7)].…”

Section: Theoretical Aspectsmentioning

confidence: 99%

“…Up to now there is not a conclusive theoretical description of these experimental results that allows us to understand how the electron-electron interaction in the atomic localized state is affecting the charge transfer and its dependence with the surface temperature. Two previous articles, by the same authors, present a theoretical description of He and Yarmoff's experiments with a limited success [6,7]. They used a model calculation based on pseudoparticle operators [8] within the finite-U noncrossing approximation [2,9,10].…”

Section: Introductionmentioning

confidence: 99%

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Signals of strong electronic correlation in ion scattering processes

Bonetto

González²,

Goldberg

2016

Phys. Rev. B

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Previous measurements of neutral atom fractions for Sr + scattered by gold polycrystalline surfaces show a singular dependence with the target temperature. There is still not a theoretical model that can properly describe the magnitude and the temperature dependence of the neutralization probabilities found. Here, we applied a first-principles quantum-mechanical theoretical formalism to describe the time-dependent scattering process. Three different electronic correlation approaches consistent with the system analyzed are used: (i) the spinless approach, where two charge channels are considered (Sr 0 and Sr + ) and the spin degeneration is neglected; (ii) the infinite-U approach, with the same charge channels (Sr 0 and Sr + ) but considering the spin degeneration; and (iii) the finite-U approach, where the first ionization and second ionization energy levels are considered very, but finitely, separated. Neutral fraction magnitudes and temperature dependence are better described by the finite-U approach, indicating that e-correlation plays a significant role in charge-transfer processes. However, none of them is able to explain the nonmonotonous temperature dependence experimentally obtained. Here, we suggest that small changes in the surface work function introduced by the target heating, and possibly not detected by experimental standard methods, could be responsible for that singular behavior. Additionally, we apply the same theoretical model using the infinite-U approximation for the Mg-Au system, obtaining an excellent description of the experimental neutral fractions measured.

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Section: Introductionmentioning

confidence: 95%

Section: Theoretical Aspectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Signals of strong electronic correlation in ion scattering processes

Bonetto

González²,

Goldberg

2016

Phys. Rev. B

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“…It is beyond the scope of this paper to review it here. Instead, we describe the Anderson-News type modeling developed at the Univer-sity Greifswald [73,74,77,78] taking a helium ion hitting an aluminum surface as an example. The description is necessarily sparse, details and data for other metals can be found in the work of Pamperin, Bronold, and Fehske [66] to which we refer as PBF.…”

Section: A Quantum Kinetic Approach To Secondary Electron Emission mentioning

confidence: 99%

Towards an integrated modeling of the plasma-solid interface

Bönitz

Filinov

Abraham

et al. 2019

Front. Chem. Sci. Eng.

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Solids facing a plasma are a common situation in many astrophysical systems and laboratory setups. Moreover, many plasma technology applications rely on the control of the plasma-surface interaction, i.e. of the particle, momentum and energy fluxes across the plasma-solid interface. However, presently often a fundamental understanding of them is missing, so most technological applications are being developed via trial and error. The reason is that the physical processes at the interface of a low-temperature plasma and a solid are extremely complex, involving a large number of elementary processes in the plasma, in the solid as well as fluxes across the interface. An accurate theoretical treatment of these processes is very difficult due to the vastly different system properties on both sides of the interface: quantum versus classical behavior of electrons in the solid and plasma, respectively; as well as the dramatically differing electron densities, length and time scales. Moreover, often the system is far from equilibrium. In the majority of plasma simulations surface processes are either neglected or treated via phenomenological parameters such as sticking coefficients, sputter rates or secondary electron emission coefficients. However, those parameters are known only in some cases and with very limited accuracy. Similarly, while surface physics simulations have often studied the impact of single ions or neutrals, so far, the influence of a plasma medium and correlations between successive impacts have not been taken into account. Such an approach, necessarily neglects the mutual influences between plasma and solid surface and cannot have predictive power.In this paper we discuss in some detail the physical processes a the plasma-solid interface which brings us to the necessity of coupled plasma-solid simulations. We briefly summarize relevant theoretical methods from solid state and surface physics that are suitable to contribute to such an approach and identify four methods. The first are mesoscopic simulations such as kinetic Monte Carlo (KMC) and molecular dynamics (MD) that are able to treat complex processes on large scales but neglect electronic effects. The second are quantum kinetic methods based on the quantum Boltzmann equation that give access to a more accurate treatment of surface processes using simplifying models for the solid. The third approach are ab initio simulations of surface process that are based on density functional theory (DFT) and time-dependent DFT. The fourths are nonequilibrium Green functions that able to treat correlation effects in the material and at the interface. The price for the increased quality is a dramatic increase of computational effort and a restriction to short time and length scales. We conclude that, presently, none of the four methods is capable of providing a complete picture of the processes at the interface. Instead, each of them provides complementary information, and we discuss possible combinations. PACS numbers:

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“…Besides the well-known twoelectron Auger processes (Ref. [55] and below) we investigated secondary electron emission due to auto-detaching negative ions [36,37] and analyzed resonant neutralization of ions with an eye on mixed-valence and Kondo resonances [38,39]. Our work on electron extraction from surfaces due to impacting atomic particles is based on multi-channel Anderson-Newns models [56] parameterized by experimental energies and target-projectile interactions deduced from considerations based on image charges [57,58].…”

Section: Electron Extractionmentioning

confidence: 99%

Electron kinetics at the plasma interface

et al. 2018

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The most fundamental response of an ionized gas to a macroscopic object is the formation of the plasma sheath. It is an electron depleted space charge region, adjacent to the object, which screens the object's negative charge arising from the accumulation of electrons from the plasma. The plasma sheath is thus the positively charged part of an electric double layer whose negatively charged part is inside the wall. In the course of the Transregional Collaborative Research Center SFB/TRR24 we investigated, from a microscopic point of view, the elementary charge transfer processes responsible for the electric double layer at a floating plasma-wall interface and made first steps towards a description of the negative part of the layer inside the wall. Below we review our work in a colloquial manner, describe possible extensions, and identify key issues which need to be resolved to make further progress in the understanding of the electron kinetics across plasma-wall interfaces.

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Mixed-valence correlations in charge-transferring atom–surface collisions

Cited by 6 publications

References 44 publications

Signals of strong electronic correlation in ion scattering processes

Signals of strong electronic correlation in ion scattering processes

Towards an integrated modeling of the plasma-solid interface

Electron kinetics at the plasma interface

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