H− survival probability during collisions with Na/Cu(111)

Yu, Song; Bahrim, B.; Makarenko, B.; Rabalais, J. W.

doi:10.1016/j.susc.2015.01.014

Cited by 6 publications

(3 citation statements)

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“…The Wave‐Packet Propagation (WPP) method adapted to ion‐surface interactions has been used to study the time evolution of the active electron involved in the ion/atom‐surface charge transfer. Briefly, the time dependent electron wave function Ψ is calculated as a solution of the time‐dependent Schrödinger equation:

\frac{italicdΨ ((),, \overset{true\to}{r}, t)}{dt} = italicHΨ ((),, \overset{true\to}{r}, t),

where H is the Hamiltonian of the system.…”

Section: Theorymentioning

confidence: 99%

“…Our previous studies have been devoted to H − formation and survival on clean and adsorbate‐covered Cu(111) surfaces. These studies have been focused on understanding the physics involved in such complex many‐body systems . In this work, we are interested to investigate the survival of both H − and H during collisions with a different copper surface exhibiting a band gap along the normal, Cu(100).…”

Section: Introductionmentioning

confidence: 99%

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Charge transfer during H/H⁻ collisions with Cu(100) and Cu(111) surfaces

Bahrim

Stafford

Makarenko

2017

Surface & Interface Analysis

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We study the H and H − survival probabilities during collisions with Cu(100) and Cu(111) surfaces, at energies ranging from 0.5 to 5 keV and exit angles ranging from 20°to 90°. Calculations are performed with the Wave-Packet Propagation method adapted to ion-surface interactions. The projectile survival probability depends on the perpendicular velocity and the copper face being investigated. Projectile's interaction time with the surface and the distance of closest approach are important factors that influence the survival. The H − survival on Cu(100) is much smaller than on Cu(111) but only at low velocities, while becoming higher or comparable to Cu(111) for higher velocities. For very fast collisions, the copper surface behaves like a jellium, and the electron involved in charge transfer does not "feel" the particularities of the surface band structure anymore. While the H survival on Cu(100) seems to not depend on energy and exit angle, the H survival on Cu (111) is both energy and angle dependent, and it is smaller. The study of partial density of states indicates that strong atom-surface interactions at short distances and the role played by surface states are important factors in determining the neutral fractions obtained after scattering. KEYWORDS charge transfer, ion fractions, ion/atom scattering, ion-surface interactions, survival probability 1 | INTRODUCTION Charge transfer processes during the interaction between atomic projectiles and metal surfaces are of both fundamental and practical interest. Such studies are crucial for progress in various applied fields, such as plasma wall interactions in fusion devices, catalysis, space science, and film deposition. 1-5 In addition, charge transfer is essential in adsorption and desorption processes, chemical reactions, quenching of metastable states, and in the ion formation during scattering and sputtering experiments. 6-10The most efficient type of charge transfer is the one-electron transfer between energetically degenerate electronic levels of the atom and the solid, also called resonant charge transfer. The atomsurface resonant charge transfer processes are very sensitive to several parameters, such as the projectile energy, exit angle, distance of closest approach to surface, and surface band structure. [11][12][13][14][15][16] In particular, it has been shown that these processes are strongly influenced by the presence of a band gap in the direction normal to the surface, such as the L-gap in the Cu(111) surface. The presence of a projected band gap in the direction normal to the surface forbids electrons with energies in that particular energy range to be transferred into the metal along the surface normal, thus strongly affecting the charge transfer processes that occur at the surface. 17,18 Our previous studies have been devoted to H − formation and survival on clean and adsorbate-covered Cu(111) surfaces. These studies have been focused on understanding the physics involved in such complex many-body systems. [18][19][20] In this work, we are inte...

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\frac{italicdΨ ((),, \overset{true\to}{r}, t)}{dt} = italicHΨ ((),, \overset{true\to}{r}, t),

where H is the Hamiltonian of the system.…”

Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Charge transfer during H/H⁻ collisions with Cu(100) and Cu(111) surfaces

Bahrim

Stafford

Makarenko

2017

Surface & Interface Analysis

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“…The formation of negative ions during the collision with metal surfaces has been extensively studied both theoretically and experimentally. − ,− Most of these studies were devoted to H – formation ,,,− ,,,,,− due to its practical relevance in plasma physics, where a high formation of negative hydrogen ions after a collision with a given surface is required. To achieve this goal, the work function of the target surface (usually W(100) or Mo(001)) is generally lowered by different degrees of Cs coverage. ,, With this method, up to 80% of H – formation is obtained …”

Section: Introductionmentioning

confidence: 99%

Band Structure Effects on the Charge Exchange Processes in H⁺ Colliding with a Cu(111) Surface

et al. 2018

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The low-energy ion scattering (LEIS) technique was used to experimentally determine the formation of positive and negative ions in the scattering of protons by a Cu(111) surface for a large scattering angle in the backscattering configuration and a wide range of incoming energies (2−8 keV). Two different collisional geometries were analyzed for a 135°fixed scattering angle: 45°/90°and 67.5°/67.5°incoming/exit angles measured with respect to the target surface. The total fraction of backscattered ions ranges from 10% to 25%, and a peculiarly high yield of negative ions, which always exceeds that of positive ions, was detected for the whole energy range analyzed. A strong dependence of the measured ion fractions with the geometrical conditions was experimentally found. On the theoretical side, a first-principles quantummechanical formalism that takes into account the three possible final charge states of the H + in a correlated way and the fine details of the band structure of the Cu(111) surface was applied to describe the charge transfer processes involved in the experimental situation. The theoretical calculation leads to a nonmonotonous dependence with the incoming energy that properly describes the experimental results, especially the negative ion fraction in the specular collisional geometry. The oscillatory behavior predicted by the theory in the range of low energies is clear evidence of the charge exchange between localized states, that is, the situation related with the presence of the surface state immersed in the L-gap present in the Cu(111) surface. The positive ion fraction is discussed for the first time for this collisional system. The differences found between the measurements and the theory seem to indicate that the neutralization to excited states and also the formation of excited negative hydrogen ions are possible charge exchange channels in the dynamic process analyzed.

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Influence of lateral configurations on the charge transfer between H− ions and Na/Ag(1 1 1) surfaces

Martinez,

Watts,

Bahrim

2024

Nuclear Instruments and Methods in Physics Research Section B:

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H− survival probability during collisions with Na/Cu(111)

Cited by 6 publications

References 28 publications

Charge transfer during H/H⁻ collisions with Cu(100) and Cu(111) surfaces

Charge transfer during H/H⁻ collisions with Cu(100) and Cu(111) surfaces

Band Structure Effects on the Charge Exchange Processes in H⁺ Colliding with a Cu(111) Surface

Influence of lateral configurations on the charge transfer between H− ions and Na/Ag(1 1 1) surfaces

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H− survival probability during collisions with Na/Cu(111)

Cited by 6 publications

References 28 publications

Charge transfer during H/H− collisions with Cu(100) and Cu(111) surfaces

Charge transfer during H/H− collisions with Cu(100) and Cu(111) surfaces

Band Structure Effects on the Charge Exchange Processes in H+ Colliding with a Cu(111) Surface

Influence of lateral configurations on the charge transfer between H− ions and Na/Ag(1 1 1) surfaces

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Product

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Charge transfer during H/H⁻ collisions with Cu(100) and Cu(111) surfaces

Charge transfer during H/H⁻ collisions with Cu(100) and Cu(111) surfaces

Band Structure Effects on the Charge Exchange Processes in H⁺ Colliding with a Cu(111) Surface