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

Lucas, A. A. and Šunjić, Marijan and Benedek, G. and Echenique, P. M. (2014) Quantum ricochets : surface capture, release and energy loss of fast ions hitting a polar surface at grazing incidence. New Journal of Physics, 16. pp. 63015-1. ISSN 1367-2630

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Abstract

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 (2000 Phys. Rev. Lett. 85 3137) for Ne+ ions ricocheting on a LiF(001) surface.

Item Type: Article
Keywords: surface channeling, ion diffraction, ion energy loss, surface optical phonons, ion skipping
Date: 2014
Subjects: NATURAL SCIENCES > Physics
Additional Information: © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 25 February 2014, revised 22 April 2014. Accepted for publication 28 April 2014. Published 9 June 2014.
Divisions: Faculty of Science > Department of Physics
Project code: 202660
Publisher: IOP Institute of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 04 Dec 2017 07:30
Last Modified: 04 Dec 2017 07:30
URI: http://digre.pmf.unizg.hr/id/eprint/5739

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