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Surface mediated photofragmentation dynamics. Theoretical approach to photoionisation, photodissociation and related processes


Hindered rotation (ie, the libration and precession of a molecule adsorbed on a surface) is demonstrated to play a role in the photoionization of adsorbates. A theoretical model has been developed including hindered rotation and the qualitative influence of this nuclear mode on photoionization spectra has been examined. First, for physisorbed species, the effect of hindered rotation is significant placing the adsorbate at the midway between a model situation where the molecule is freely moving in the gas phase and a molecule frozen in space. Second, for the chemisorbed species the influence of hindered rotation shows up as a measurable modification of the angular distribution of electrons and the model is able to account for the experimentally observed temperature effects on the photoionization spectra. Finally, a recipe connecting the angle (mean angle in the quantum mechanical sense) between the molecular axis and the surface normal and the photoionization cross section has been constructed. Using experimental data this recipe will allow a better estimation of the position of the molecule on the surface.

Funding Scheme

CSC - Cost-sharing contracts


Bètiment 210 - Université Paris-sud
91405 Gometz La Ville