Electronic energy loss of low velocity H+ beams in Al, Ag, Sb, Au and Bi

Valdés, Joaquín; Tamayo, G.aMartínez; Lantschner, G. H.; Eckardt, J. C.; Arista, N. R.

doi:10.1016/0168-583x(93)95744-p

Cited by 70 publications

(27 citation statements)

References 28 publications

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“…Additionally, significant vicinage effects [33] on " can be ruled out in the present investigation. Our results are in very good agreement with earlier measurements [27] (open squares) and at the same time extend the range, where " / v is observed, by a factor of 2 towards lower energies. For H projectiles, our data are in perfect agreement with theoretical calculations for a FEG [34,35] with a density parameter r s of 2.13, appropriate for Al [36] (gray dotted line).…”

supporting

confidence: 94%

“…Electronic SCS of H, D, and He ions in Al as a function of velocity. Also shown are data from [27,37]. Predictions from DFT for slow H and He in a FEG are shown as dotted and dashed gray lines, respectively [34,35].…”

mentioning

confidence: 98%

“…Al was deposited in situ on the substrate; two sets of samples were investigated with thicknesses of 2.1 and 4.2 nm (0.565 and 1:13 g=cm 2 ). Thicknesses of Al layers were obtained using reference stopping power values for protons at sufficiently large ion velocities (v > 0:4 a:u:, i.e., at proton energies >5 keV) [27]. Note that at these energies nuclear energy losses hardly contribute to the energy loss and, therefore, do not influence the results presented below [5].…”

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confidence: 99%

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Electronic Excitations of Slow Ions in a Free Electron Gas Metal: Evidence for Charge Exchange Effects

et al. 2011

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Electronic energy loss of light ions transmitted through nanometer films of Al has been studied at very low ion velocities. For hydrogen, the electronic stopping power S is found to be perfectly proportional to velocity, as expected for a free electron gas. For He, the same is anticipated, but S shows a transition between two distinct regimes, in both of which S is velocity proportional-however, with remarkably different slopes. This finding can be explained as a consequence of charge exchange in close encounters between He and Al atoms, which represents an additional energy loss channel.

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confidence: 94%

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confidence: 98%

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confidence: 99%

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Electronic Excitations of Slow Ions in a Free Electron Gas Metal: Evidence for Charge Exchange Effects

et al. 2011

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“…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 proportionality coefficient with the projectile's atomic number Z has been verified [6] and reproduced by ab initio atomistic simulations [14].…”

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confidence: 99%

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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“…henceforth) [14]. This simple relation has been verified experimentally in many sp-bonded metals [16][17][18][19].…”

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confidence: 96%

Ab initioelectronic stopping power and threshold effect of channeled slow light ions inHfO2

Wang

Liao

et al. 2017

Phys. Rev. B

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We present ab initio study of the electronic stopping power of protons and helium ions in an insulating material, HfO2. The calculations are carried out in channeling conditions with different impact parameters by employing Ehrenfest dynamics and real-time, time-dependent density functional theory. The satisfactory comparison with available experiments demonstrates that this approach provides an accurate description of electronic stopping power. The velocity-proportional stopping power is predicted for protons and helium ions in the low energy region, which conforms the linear response theory. Due to the existence of wide band gap, a threshold effect in extremely low velocity regime below excitation is expected. For protons, the threshold velocity is observable, while it does not appear in helium ions case. This indicates the existence of extra energy loss channels beyond the electron-hole pair excitation when helium ions are moving through the crystal. To analyze it, we checked the charge state of the moving projectiles and an explicit charge exchange behavior between the ions and host atoms is found. The missing threshold effect for helium ions is attributed to the charge transfer, which also contributes to energy loss of the ion.

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Electronic energy loss of low velocity H+ beams in Al, Ag, Sb, Au and Bi

Cited by 70 publications

References 28 publications

Electronic Excitations of Slow Ions in a Free Electron Gas Metal: Evidence for Charge Exchange Effects

Electronic Excitations of Slow Ions in a Free Electron Gas Metal: Evidence for Charge Exchange Effects

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

Ab initioelectronic stopping power and threshold effect of channeled slow light ions inHfO2

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