The role of the initial population of molecular vibrations in surface photochemistry Original Research Article

In a one-dimensional wavepacket study the role of thermal population of molecular vibrations within surface photochemistry is studied using a model potential adopted to the system NO/Cr2O3(0001). Simulations are made concerning the temperature dependence of the efficiency for UV-laser induced desorption and of velocity distributions. The course of these observables as a function of temperature is strongly dependent on the lifetime of the excited state. The results are compared with experimental results on the temperature dependence of the non-thermal desorption of NO from the Cr2O3(0001) surface after excitation at 6.4 eV. The experimentally observed increase of desorption cross-sections by about a factor of 2 when changing the surface temperature between 100 and 300 K is simulated when assuming an average resonance lifetime on the order of 10 fs. The experimentally found increase of translational energy with increasing surface temperature by ∼100 m/s is also consistent with theoretical results.