Electronic interaction of very slow light ions in Au: Electronic stopping and electron emission

Markin, S.N.; Primetzhofer, Daniel; Průša, Stanislav; Brunmayr, Michael; Kowarik, G.; Aumayr, F.; Bauer, Péter

doi:10.1103/physrevb.78.195122

Cited by 66 publications

(47 citation statements)

References 28 publications

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“…We find very good quantitative agreement with some recent low energy ion scattering experiments on thin gold films [2][3][4]. The results are analyzed in terms of the electronic excitations that are responsible for the energy loss, which very clearly shows why the slope of S e increases with projectile velocity.…”

supporting

confidence: 72%

“…1 shows our results for S e (v) for H and He projectiles in gold for the velocity range v = 0.06−0.50 a.u. We also plot results of some recent experiments performed on thin single crystal gold films oriented along 100 [2] and polycrystalline gold films [3,4]. The agreement between our simulations and the experiments is noticeable.…”

supporting

confidence: 54%

“…Experiments on noble metals Cu, Ag and Au, show pronounced nonlinearities in S e (v) [2-4, 8, 11, 15, 19]. In the case of slow H and He ions in gold [2][3][4], S e (v) displays an increase in the slope roughly around v 0.18 a.u. This is usually attributed to a threshold projectile velocity needed to excite the d-band electrons that are relatively tightly bound.…”

mentioning

confidence: 99%

“…Substantial progress has been made for weakly non-adiabatic problems such as the chemistry of vibrationally excited molecules landing on metal surfaces [1], but not in the stronger coupling regime of radiation damage. Recently, the electronic stopping power for swift ions in gold has been carefully characterized by experiments [2][3][4], showing flagrant discrepancies with the established paradigm for such problems [5,6], and only qualitative agreement with time-dependent tight-binding studies [7], and with detailed studies for protons based on first principles [8], leaving very fundamental questions unanswered in spite of the apparent simplicity of the system. Most notably the H/He anomaly: the present understanding predicts a stopping power for H higher than for He at low velocities [6], which strongly contradicts the recent experiments [4].…”

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confidence: 99%

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Electronic Stopping Power in Gold: The Role ofdElectrons and theH/HeAnomaly

et al. 2012

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The electronic stopping power of H and He moving through gold is obtained to high accuracy using time-evolving density-functional theory, thereby bringing usual first-principles accuracies into this kind of strongly coupled, continuum non-adiabatic processes in condensed matter. The two key unexplained features of what observed experimentally have been reproduced and understood: (i) The non-linear behaviour of stopping power versus velocity is a gradual crossover as excitations tail into the d-electron spectrum; and (ii) the low-velocity H/He anomaly (the relative stopping powers are contrary to established theory) is explained by the substantial involvement of the d electrons in the screening of the projectile even at the lowest velocities where the energy loss is generated by s-like electron-hole pair formation only.Non-adiabatic processes are at the heart of aspects of science and technology as important as radiation damage of materials in the nuclear and space industries, and radiotherapy in medicine. Yet, in spite of a long history, the quantitative understanding of non-adiabatic processes in condensed matter and our ability to perform predictive theoretical simulations of processes coupling many adiabatic energy surfaces is very much behind what accomplished for adiabatic situations, for which first-principles calculations provide predictions of varied properties within a few percent accuracy. Substantial progress has been made for weakly non-adiabatic problems such as the chemistry of vibrationally excited molecules landing on metal surfaces [1], but not in the stronger coupling regime of radiation damage. Recently, the electronic stopping power for swift ions in gold has been carefully characterized by experiments [2-4], showing flagrant discrepancies with the established paradigm for such problems [5,6], and only qualitative agreement with time-dependent tight-binding studies [7], and with detailed studies for protons based on first principles [8], leaving very fundamental questions unanswered in spite of the apparent simplicity of the system. Most notably the H/He anomaly: the present understanding predicts a stopping power for H higher than for He at low velocities [6], which strongly contradicts the recent experiments [4].A particle moving through a solid material interacts with it and loses its kinetic energy to both the nuclei and the electrons inside it. At projectile velocities between 0.1 and 1 atomic units (a.u. henceforth) both the nuclear and the electronic contributions to the stopping power (energy lost by the projectile per unit length) are sizeable [7]. Based on the jellium model (homogeneous electron gas) the electronic stopping power, S e , is predicted to be S e ∝ v for a slow projectile traversing a metallic medium [9,10]. Such behaviour has been observed experimentally in many sp-bonded metals [11,12], and the jellium model has allowed deep understanding of the dynamic screening of the projectile and its relation to stopping [13]. Even the jellium prediction of an oscillation of the ...

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supporting

confidence: 72%

supporting

confidence: 54%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Electronic Stopping Power in Gold: The Role ofdElectrons and theH/HeAnomaly

et al. 2012

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“…In fact, the main experimental difficulties at low energies arise from the greater influence of target roughness due to the requirement of using very thin targets, leading to disadvantageous roughness to thickness ratios. For this reason, although there are several accurate measurements of stopping powers down to very low energies ($1-2 keV) [2][3][4][5][6][7][8][9][10][11], there are very few experimental determinations of straggling values for energies below 10 keV [12]. Also, as shown by Konac et al [12], there are significant discrepancies in low-energy straggling data reported by different groups, which gradually disappear at larger energies.…”

Section: Introductionmentioning

confidence: 86%