Influence of Band Width on the Scattered Ion Yield Spectra of a He⁺Ion by Resonant or Quasi-Resonant Charge Exchange Neutralization

Abstract

The influence of the band structure, especially the bandwidth, on the scattered ion yield spectra of a He + ion by the resonant or quasi-resonant neutralization was theoretically examined using quantum rate equations. When calculating the scattered ion yield spectra of He + to simulate the experimental data, we observed that the band structure, especially the bandwidth, had a strong influence on the spectra at relatively low incident He reproduce nor account for such spectra. Furthermore, the calculated ion survival probability (ISP) at low incident ion energies tended to decrease with increasing bandwidth. This decrease in ISP probably corresponds to the relatively small scattered ion yield usually observed at low incident ion energies.Theoretically, such a decrease indicates that a He + ion with a low incident energy can be easily neutralized on the surface when the bandwidth is large.

Quasi-resonant neutralization of He+ions at a germanium surface

“…For the energy-dependent amplitude of the oscillations, a + (E), a Gaussian shape was assumed on the basis that the largest amplitude is observed at ∼3 keV; at lower and higher energies damping maybe expected due to AN and due to resonant processes, respectively. The oscillation velocity v osc ≈ 1.41 × 10 6 m s −1 and the phase shift φ ≈ −0.9 characterize the observed oscillations, in good quantitative agreement with earlier experiments [25]. The influence of resonant charge exchange in close collisions, P + RN , is globally taken into account by lowering P + at energies above th by use of a Fermi-Dirac distribution function.…”

“…7 (solid line) From this simple model hardly any detailed information for the individual processes can be deduced. A more advanced theory should include the following key quantities [21,23,25]: (1) The mismatch in energy between the He ground state and the Ge d-band…”

“…From this simple model hardly any detailed information for the individual processes can be deduced. A more advanced theory should include the following key quantities [21,23,25].…”

“…approach of Tolk et al leads to at least qualitative agreement with experimental data. Since then, various efforts have been dedicated to obtaining a more detailed understanding of qRN [20][21][22][23][24][25].…”

Highly Sensitive Detection of Surface and Intercalated Impurities in Graphene by LEIS

“…Hence both the time for destructive interference and the short lifetime of the hole in the valence band scale with the reciprocal of the bandwidth. This dependence has also been found by Kondo using quantum rate equations, although his results were for primary energies below 1 keV. The exceptionally strong neutralization of helium ions by graphite and graphene is thus the result of the fact that the band of graphene (and graphite) extends to such low energies that it is in (or nearly in) energy resonance with the He 1s level (Figure ).…”