Spot-beam effect in grazing atom-surface collisions: from quantum to classical

MIRAGLIA, J E; GRAVIELLE, M S; FRISCO, L

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Año: 2018 vol. 30 p. 405001 - 405008

0953-8984

p { margin-bottom: 0.25cm; line-height: 120%; }Grazing incidencefast atom diffraction (GIFAD) is a sensitive tool for surfaceanalysis, which strongly relies on the quantum coherence of theincident beam. In this article we study the spot-beam effect, due tocontributions coming from different positions of the focus point ofthe incident particles, which affects the coherence of GIFADspectra. We show that the influence of the spot-beam effect on GIFADpatterns depends on the width of the surface area that is coherentlylighted by the atomic beam. While for extended illuminations thespot-beam contribution plays a minor role, when a narrow surfacearea is coherently lighted, the spot-beam effect allows projectilesto explore different zones of a single crystallographic channel,bringing to light intra-channel interference structures. In thislast case the spot-beam effect gives also rise to a non-coherentbackground, which deteriorates the visibility of the interferencestructures. We found that by varying the impact energy, whilekeeping the same collimating setup, it is possible to switchgradually from quantum to classical projectile distributions.Present results are compared with available experimental data,making evident that the inclusion of focusing effects is necessaryfor the proper theoretical description of the experimental spectra.