Naslov
Quantum ricochets : surface capture, release and energy loss of fast ions hitting a polar surface at grazing incidence

Autori
Lucas, A.A. ; Šunjić, Marijan ; Benedek, G. ; Echenique, P.M.

Izvornik
New journal of physics (1367-2630) 16 (2014); 063015-1

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
surface channeling; ion diffraction; ion energy loss; ion skipping; surface optical phonons
(surface channeling; ion diffraction; ion energy loss; ion skipping; surface optical phonon)

Sažetak
A diffraction mechanism is proposed for the capture, multiple bouncing and final escape of an energetic ion impinging on the surface of a polarizable material at grazing incidence. Capture and escape are effected by elastic diffraction consisting in the exchange of a parallel surface wave vector G = 2/a between the ion and the surface lattice (of lattice constant a along the ion path). Diffraction- assisted capture becomes possible only for glancing angles smaller than a critical value given by – |Vim|/E, where E is the ion kinetic energy, h/Mv its de Broglie wavelength, and Vim the electronic image potential at the distance from the surface where diffraction occurs. The ion can fall into a I would avoid discussion of resonances etc and just put bound state in the quasi- continuous spectrum of its image potential and execute one or several bounces before being released by the time reverse diffraction process. The single-bounce length LB = Toscv parallel to the surface is quantized by the duration of one oscillation of the ion between the classical turning points of the image potential at the selected bound state energy. The capture, bouncing motion and escape are accompanied by a large, oscillatory energy loss in the forward motion of several tens of eV caused by the coherent emission of a giant number of quanta of Fuchs-Kliewer surface phonons characteristic of the polar material. An analytical calculation of the energy loss spectrum, based on the model ion-phonon coupling developed earlier, is presented which fully explains the experimental spectrum of Villette et al [1].

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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