Surface-induced vibrational excitation of metastable nitrogen molecules traversing a micro-slit copper grating: a probe of surface profiles

The interaction at mean distance (a few tens up to a few hundreds of a0), i.e. in the van der Waals interaction range, between metastable nitrogen molecules, N2* (A3Sigmau+), and the slit edges of a micro-slit copper grating depends on both the molecular orientation and the internuclear distance in the molecule. Such an interaction is able to induce rotational and vibrational transitions. Endo-energetic transitions (v - > v + 1, v ranging from 5 to 10) are observed by means of a time-of-flight technique combined with an angular distribution measurement. By setting the grating plane at an angle with respect to the incident direction, different from that imposed by ideally planar slit walls, it is shown that the angular distribution of the inelastic process reveals a departure of the surface from an ideal plane. Assuming a regular evolution of the tangent plane along the surface profile, a mean wall profile can be derived from this distribution.