Endothermal fine-structure transition of metastable argon atoms passing through a micro-slit copper grating

Laboratoire de Physique des Lasers (CNRS-UMR 7538), Université Paris 13 Avenue J. B. Clément, 93430 Villetaneuse, France

Corresponding author: baudon@lpl.univ-paris13.fr

Received: 8 April 2002
Accepted: 24 July 2002

Abstract

The endothermal fine-structure transition ( —175 ) of metastable argon atoms traversing at a velocity of 1030 a micro-slit copper grating the normal axis of which is set, in a first configuration, at with respect to the incident beam axis, is observed. The related differential cross-section (DCS) is sharply peaked at and its velocity dependence reveals the expected threshold at 900. In a second configuration, the grating is set at an angle of , allowing for a 7% transmission of the incident beam. Atoms elastically scattered by the corner edges of the grating slits are observed in the angular range – and the elastic DCS is measured in relative values. In spite of such a widely unsuited geometry, the endothermal process still appears (with a magnitude 10 times smaller than before), because of the surface corrugation. The inelastic DCS is now peaked at with a width of about , as predicted from the corrugation angle distribution deduced from the inelastic DCS of metastable molecules traversing the same grating.