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Abstract

Irradiation of a NO covered NiO surface by UV photons (hv=5.0and 6.4 eV, respectively) yields desorption with a quantum yield of the order 10⁻². Fully state-resolved determination of the energy distributions of the desorbing particles were performed by means of laser-induced fluorescence and demonstrated the non-thermal origin of at least part of them. Bimodal velocity distributions, a pronounced spin-orbit selectivity for molecules with low rotational levels, and an increase of the mean translational energy with increasing rotational energy are the most remarkable effects observed. The results are qualitatively discussed on the basis of current concepts for desorption via electronic excitation and for scattering of open-shell molecules at surfaces.