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

Scientific paper - Original scientific paper

• Author: A. A. Lucas
• Author: Marijan Šunjić
• Author: G. Benedek
• Author: P. M. Echenique
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

A diffraction mechanism is proposed for the capture, multiple bouncing and final escape of a fast ion (keV) impinging on the surface of a polarizable material at grazing incidence. Capture and escape are effected by elastic quantum diffraction consisting of the exchange of a parallel surface wave vector G = 2π/a between the ion parallel momentum and the surface periodic potential of period a. Diffraction-assisted capture becomes possible for glancing angles Φ smaller than a critical value given by Φ c2 ≈ 2λ/a–|V im|/E, where E is the kinetic energy of the ion, λ = h/Mv its de Broglie wavelength and V im its average electronic image potential at the distance from the surface where diffraction takes place. For Φ < Φ c, the ion can fall into a selected capture state in the quasi-continuous spectrum of its image potential and execute one or several ricochets before being released by the time reversed diffraction process. The capture, ricochet and escape are accompanied by a large, periodic energy loss of several tens of eV in the forward motion caused by the coherent emission of a giant number of quanta ħω of Fuchs–Kliewer surface phonons characteristic of the polar material. An analytical calculation of the energy loss spectrum, based on the proposed diffraction process and using a model ion–phonon coupling developed earlier (Lucas et al 2013 J. Phys.: Condens. Matter 25 355009), 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.

• Keywords (english): surface channeling; ion diffraction; ion energy loss; surface optical phonons; ion skipping
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: New Journal of Physics
• Numbering: vol. 16, 063015
• e-ISSN: 1367-2630
• DOI: https://doi.org/10.1088/1367-2630/16/6/063015
• URN:NBN: urn:nbn:hr:217:891986
• Publication: 2014
• Document URL: https://iopscience.iop.org/article/10.1088/1367-2630/16/6/063015
• Type of resource: Text
• Access conditions: Open access
• Public note: © 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.
• Created on: 2019-11-27 21:56:20