Threshold effect in the energy loss of slow protons and deuterons channeled in Au crystals

Figueroa, E.; Cantero, E. D.; Eckardt, J. C.; Lantschner, G. H.; Valdés, Joaquín; Arista, N. R.

doi:10.1103/physreva.75.010901

Cited by 46 publications

(21 citation statements)

References 16 publications

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“…[20][21][22][23] For all noble metals at proton velocities ∼0.2 a.u., S is observed to become velocity proportional again. The velocity for which the transition between different regimes is observed depends on the binding energy of the d states, [24][25][26] which gives confidence in the interpretation of the velocity scaling of ε for protons due to the nontrivial density of states in noble metals.…”

Section: Introductionmentioning

confidence: 69%

Inelastic energy loss of medium energy H and He ions in Au and Pt: Deviations from velocity proportionality

Primetzhofer

2012

Phys. Rev. B

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Electronic energy loss of light ions in nm films of Au and Pt has been studied at keV ion energies. For H the electronic stopping power S is found to exhibit the expected velocity proportionality at low ion velocities, which confirms the anticipated excitation mechanisms responsible for the energy transfer between ions and the electrons in the solid. In contrast, for He, S shows a clear deviation from velocity proportionality for both materials at ion velocities below 0.8 atomic units, i.e., 64 keV. This result indicates a change in the interaction mechanisms active at the investigated ion velocities, which cannot exclusively be interpreted from the density of states of the target. Instead, the more complex electronic structure of the He ion enables an additional energy loss channel due to charge exchange by atomic level promotion. Associated energy losses together with a changed equilibrium charge state permit an explanation of the observed phenomenon.

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Section: Introductionmentioning

confidence: 69%

Inelastic energy loss of medium energy H and He ions in Au and Pt: Deviations from velocity proportionality

Primetzhofer

2012

Phys. Rev. B

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“…Furthermore, some previous studies with a similar methodology have resulted in a nonlinear velocity scaling of ε that is different from the modeling in the program and that was in excellent agreement with other results obtained in transmission (compare, for example, Refs. [19] and [20] as well as Refs. [22] and [23]).…”

Section: Experiments and Evaluationmentioning

confidence: 83%

“…Indeed, many investigated systems have been found to show this behavior; for metals with occupied electronic states up to the Fermi level E F and unoccupied states available directly above E F this can be also well understood. Due to the excitation thresholds of certain electronic states and the limited maximum energy transfer in a binary collision, pronounced deviations have been found at sufficiently low energies, i.e., below 10 keV for protons or ß25 keV for He ions, for some noble metals and semiconducting and insulating materials [18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Electronic interactions of medium-energy ions in hafnium dioxide

Primetzhofer

2014

Phys. Rev. A

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In this article, the electronic interaction of medium-energy ions with hafnium dioxide is studied. Stopping cross sections for He ions in the energy range from 30 to 160 keV have been measured in backscattering experiments from thin films of HfO 2 on Si using time-of-flight medium-energy ion scattering. The observed energy loss for helium ions is found to be high compared to expectations from earlier results for hydrogen in HfO 2 , a result which indicates a contribution from energy-loss processes that is different from direct excitation of electron-hole pairs in close collisions. Furthermore, data exhibit a significant deviation from velocity proportionality. A discussion of the results, together with data from studies for H and He in SiO 2 , show characteristic differences which are traced back to different electronic structures of the target materials and their influence on the charge-exchange channels that are active in the interaction with helium. Charge exchange, in turn, via shifted mean-charge states, will influence the observed ionization along the ion track. The results can furthermore serve as reference values for ion-beam-based depth profiling at medium and low ion energies.

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“…A similar increase in the S e gradient at velocities between 0.3 and 0.5 a.u. has been seen in experiments for various systems: protons in Au 52,53 , He in Al 54 , and protons and He in Cu 55 , to name a few. The change in gradient for the Cu and Au experiments is suggested to be a result of interactions with the target's 3d and 5d electrons in Cu and Au respectively at higher projectile velocities, where a minimum energy transfer is required for the excitation of d electrons in both metals 52 .…”

Section: Low Velocitymentioning

confidence: 95%

Anisotropy of electronic stopping power in graphite

Halliday

Artacho

2019

Phys. Rev. B

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The rate of energy transfer from ion projectiles onto the electrons of a solid target is hard to determine experimentally in the velocity regime between the adiabatic limit and the Bragg peak. First-principles simulations have lately offered relevant new insights and quantitative information for prototypical homogeneous materials. Here we study the influence of structural anisotropy on electronic stopping power with time-dependent density functional theory simulations of a hydrogen projectile in graphite. The projectile travelled at a range of angles and impact parameters for velocities between 0.1 and 1.4 a.u., and the electronic stopping power was calculated for each simulation. After validation with average experimental data, the anisotropic crystal structure was found to have a strong influence on the stopping power, with a difference between simulations parallel and perpendicular to the graphite plane of up to 25%, more anisotropic than expected based on previous work. The velocity dependence at low velocity displays clear linear behaviour in general, except for projectiles travelling perpendicular to graphitic layers, for which a threshold-like behaviour is obtained. For projectiles travelling along graphitic planes metallic behaviour is observed with a change of slope when the projectile velocity reaches the Fermi velocity of the electrons.

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Threshold effect in the energy loss of slow protons and deuterons channeled in Au crystals

Cited by 46 publications

References 16 publications

Inelastic energy loss of medium energy H and He ions in Au and Pt: Deviations from velocity proportionality

Inelastic energy loss of medium energy H and He ions in Au and Pt: Deviations from velocity proportionality

Electronic interactions of medium-energy ions in hafnium dioxide

Anisotropy of electronic stopping power in graphite

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