Fast Ion Surface Energy Loss and Straggling in the Surface Wake Fields

Nandi, T.; Haris, K.; Hala,; Singh, Gurjeet; Kumar, Pankaj; Kumar, Rajesh; Saini, Santosh Kumar; Khan, Saif; Jhingan, A.; Verma, Pooja; Tauheed, A.; Mehta, D.; Berry, H. G.

doi:10.1103/physrevlett.110.163203

Cited by 13 publications

(16 citation statements)

References 25 publications

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“…Whereas, the distinction between the measurements through the K-REC peak and the empirical results discerns that the REC process is one of the important chargeexchange processes originating at the surface; the role of dynamic screening and wake effects may be vital. The processes at the exit surface of the foil may include the formation of excited projectile bound states as high as Rydberg states due to nonradiative electron capture and wake riding electron capture to circular Rydberg states [13,14] occurred because of finite surface wake field produced right at the exit surface [15,29]. The electrons, captured at such high-lying Rydberg states, are quite longlived and therefore can be detected with the electromagnetic techniques.…”

Section: Resultsmentioning

confidence: 99%

“…Several physical processes originating from the solid surfaces, for example, wake riding electron capture [13] leading to the formation of circular Rydberg states [14], electron capture in low-lying and high-lying states, etc., contribute in the dynamicity of the charge-changing processes. The excited states produced by any of the above processes can be further affected by the surface energy loss field (SELF) at the exit surface [15]. These charge-changing processes can be investigated through the distribution of charge state fractions (CSF) called charge state distribution (CSD) for both experiments and theories.…”

Section: Introductionmentioning

confidence: 99%

“…Note that the theoretical predictions make use of the incident charge state values because of the fact that the post-collision charge states are equal to the incident charge states. The stopping power of the ions passing through the thin carbon foils mostly depends on the ion-solid interactions in the bulk of the foil as the stopping power at the solid surface is comparatively very small [15]. Hence, the charge state information in the bulk of the foil is essential to estimate the stopping power correctly at the bulk, and such information can be available from experiments as the present one.…”

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confidence: 98%

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Disentangling the bulk and exit surface contribution on projectile-charge-state evolution

Sharma

Nandi

2019

Phys. Rev. Accel. Beams

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Charge state evolution of the projectile ions while traversing through the solid target medium has been explored using the radiative electron capture process. The measured centroid energies of the convoluted radiative electron capture peak structures have been used to determine the mean K-shell binding energies and mean charge state of the projectile ions. It has been observed that the mean charge states of present measurements are lower than the earlier measurements done using the characteristic K α x-ray transitions. The difference is due to the capture of target electrons in the inner-shell vacancies, created during the collision process, of projectile ions. Further, the measured mean charge states are compared with the empirical predictions. A significant discrepancy between experimental and theoretical values has been observed, which is attributed to the multielectron capture by projectile ions due to nonradiative electron capture process from the exit surface while exiting from the foil. The significant variation between mean charge state values obtained from different tools provides a clear indication of the dynamic nature of the charge-changing mechanism at different regions (entrance surface, bulk, and exit surface) of the ion-solid interaction. The present results can be used to validate the departure between the theory and experiment on the charge state dependent stopping powers.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 98%

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Disentangling the bulk and exit surface contribution on projectile-charge-state evolution

Sharma

Nandi

2019

Phys. Rev. Accel. Beams

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“…However, this fact was not known and mistakenly, CSD-O had been used in place of CSD-I [1] in studying inner shell ionization. Note that the innershell ionization of target atoms taking place inside the target, circular Rydberg state forming near the exit surface [2], ion energy-loss mostly happening inside the target and further modified in the exit surface [3] etc. demands the knowledge of CSD-I.…”

Section: Introductionmentioning

confidence: 99%

Exploring a novel model for projectile charge state distribution inside a solid-target

Chatterjee,

Sharma,

Mitra

et al. 2021

Preprint

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For the first time, we report a theoretical methodology to predict charge state distribution of projectile ions inside a solid-target. The method utilizes either a simple Fermi gas model or an ab initio theoretical method and a certain parameterization of width for the Lorentzian charge state distributions. Results obtained from the two approaches are comparable, but the former has a certain edge over the latter. The projectile charge state distribution inside a solid-target plays a significant role in estimating electron capture cross-sections and then to describe the observed Kshell ionization dynamics. The electron capture process plays a certain role in L-shell ionization dynamics too, but in a test case of Si on Au target the subshell charge sharing contributes a more vital role than the electron capture. Thus, we have validated the present model as a reliable as well as useful for many solid-target based applications viz. tumour therapy, biophysics, accelerators, material science etc.

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“…The occurrence of the wake effect was also studied on solid surfaces, both in theoretical works [7,8] and in experiments [9,10], which demonstrated vicinage effects in the Coulomb explosion and energy loss of diatomic molecules grazingly scattered on crystal surfaces. In the more recent experiments, it was shown that the surface wake also plays a role in the energy loss and straggling of fast ions traversing a dielectric boundary [11] and that it affects the formation of circular Rydberg states in beam-foil experiments [12]. While the above studies were concerned with the wake due to electronic collective modes in solids and their surfaces, there were several studies addressing the role of the wake due to the excitation of the Fuchs-Kliewer (FK) or optical surface phonon modes in ion scattering from polar surfaces [13,14].…”

Section: Introductionmentioning

confidence: 99%

Wake potential in graphene-insulator-graphene composite systems

et al. 2019

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We study the wake potential produced by an external charged particle that moves parallel to various sy 1-Al 2 O 3-sy 2 sandwich-like composites, where the system sy i (with i = 1, 2) may be vacuum, pristine graphene, or doped graphene. The effective dielectric function of the composites is obtained using three complementary methods for graphene's electronic response, based on the massless Dirac fermions (MDF) method, the extended hydrodynamic (eHD) model, and the ab initio approach. Three velocity regimes are explored with respect to the threshold for excitations of the Dirac plasmon in graphene, given by its Fermi velocity v F. In the low-velocity regime (below v F), only the transverse optical (TO) phonons in the Al 2 O 3 layer contribute to the wake potential in the surface with sy 2 (which is nearest to the charged particle), in a manner that is only sensitive to the composition of that system: if sy 2 is vacuum, the TO phonons give rise to intense oscillations in the wake potential, which are strongly suppressed if sy 2 is pristine or doped graphene. For intermediate velocities (above v F), the hybridized plasmon-TO phonon modes on both surfaces contribute to the wake potential in the surface with sy 2 , with the most dominant contribution coming from the hybridized Dirac-like plasmonic modes. In the high-velocity regime (well above v F), the highest-lying hybridized Dirac plasmon gives the dominant contribution to the wake potential, which exhibits a typical V-shaped wave-front pattern that lags behind the charged particle. It is found that the MDF method agrees very well with the results of the ab initio method for small and intermediate velocities. However, in the high-velocity regime, the high-energy π plasmon in graphene introduces new features in the wake potential in the form of fast oscillations, just behind the charged particle. Those oscillations in the wake potential are well described by both the eHD and the ab initio method, proving that the π plasmon indeed behaves as a collective mode.

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Fast Ion Surface Energy Loss and Straggling in the Surface Wake Fields

Cited by 13 publications

References 25 publications

Disentangling the bulk and exit surface contribution on projectile-charge-state evolution

Disentangling the bulk and exit surface contribution on projectile-charge-state evolution

Exploring a novel model for projectile charge state distribution inside a solid-target

Wake potential in graphene-insulator-graphene composite systems

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