THE ROLE OF THE INITIAL POPULATION OF MOLECULAR VIBRATIONS IN SURFACEPHOTOCHEMISTRY

In a one-dimensional wavepacket study the role of thermal population o f molecular vibrations within surface photochemistry is studied using a model potential adopted to the system NO/Cr2O3(0001). Simulations ar e made concerning the temperature dependence of the efficiency for W-l aser induced desorption and of velocity distributions. The course of t hese observables as a function of temperature is strongly dependent on the lifetime of the excited state. The results are compared with expe rimental results on the temperature dependence of the non-thermal deso rption of NO from the Cr2O3(0001) surface after excitation at 6.4 eV. The experimentally observed increase of desorption cross-sections by a bout a factor of 2 when changing the surface temperature between 100 a nd 300 K is simulated when assuming an average resonance lifetime on t he order of 10 fs. The experimentally found increase of translational energy with increasing surface temperature by similar to 100 m/s is al so consistent with theoretical results. (C) 1998 Elsevier Science B.V.