Journal of Chemical Physics, Vol.107, No.10, 3999-4005, 1997
Rotational- and vibrational-state resolved HF-surface interactions investigated by surface light-induced drift
Experiments using surface light-induced drift are performed to yield information on the rotational (J) and vibrational (v) state dependence of molecule-surface interactions. Data are presented for the change in accommodation coefficient for tangential momentum transfer alpha upon excitation of HF interacting with a polycrystalline LiF surface (on a Cu substrate) and a hydrophobic stearic-acid monolayer (on a stainless-steel substrate). We employed both P- and R-branch excitation of HF in the fundamental vibrational band (v=0-->1) with J=0-4, using a continuously tunable color-center laser (lambda approximate to 2.5 mu m). By combining the results for the P-and R-branch, we find that the influences of J and v upon the molecule-surface interaction can be considered independent to a good approximation. It is found that a decreases upon vibrational excitation v=0-->1, whereas it increases with increasing J. The J and v dependences of alpha are discussed in the framework of a unified kinetic theory of molecule-surface interaction. (C) 1997 American Institute of Physics.