UV laser-induced desorption of CO from Cr 2O 3(111). A fully quantum state resolved mapping of the desorbing species

Abstract

The laser-induced desorption of CO adsorbed on an epitaxially grown film of Cr 2O 3(111) has been studied using 193 nm (6.4 eV) laser light. The velocity flux distributions of the desorbing neutral CO in its ground electronic state were recorded quantum state specifically by making use of a (1 + 1′) REMPI (resonance enhanced multiphoton ionization) technique. Single rovibrational states of the desorbing CO could be selected by using the (B 1Σ + ← X 1Σ +) transition in the VUV at ≈ 115 nm for the first excitation step of the REMPI process. Excellent resolution was obtained in contrast to the most commonly used (2 + 1) REMPI process for the same intermediate state. The velocity flux distributions were bimodal for ν″ = 0 and monomodal for ν″ = 1. The high desorption cross section of (3.5 ± 1) × 10 −17 cm 2 is typical for the desorption from oxide surfaces.