Fast ion diffraction of protons on NaCl, the discovery of GIFAD

TL;DR

This paper recounts the discovery of GIFAD, a technique for analyzing crystal surfaces at the atomic level using fast atom diffraction, highlighting its unexpected quantum phenomena observed with keV protons.

Contribution

It documents the historical development and discovery of GIFAD, emphasizing the role of curiosity and prior groundwork in revealing quantum behaviors of keV atoms.

Findings

Identification of diffraction spots in GIFAD

Observation of supernumerary rainbows at keV energies

Recognition of quantum behavior in fast atom-surface interactions

Abstract

Grazing incidence fast atom diffraction (GIFAD or FAD) has become a technique to track the surface topology of crystal surface at the atomic scale. The paper retraces the events that led to the discovery of unexpected quantum behavior of keV atoms during the thesis of Patrick Rousseau in Orsay and Andreas Schueller in Berlin. In Orsay, it started by diffraction spots whereas in Berlin supernumerary rainbows were first identified at keV. Though the discovery was not anticipated, it did not take place by accident, everything was in place several years before, waiting only for an interest in neutral projectiles with a touch of curiosity.