DYNAMICAL STUDIES OF UV-LASER-INDUCED NO-DESORPTION FROM THE POLAR NIO(111) VERSUS THE NONPOLAR NIO(100) SURFACES

We have studied the UV-laser-induced desorption of NO adsorbed on an e pitaxial film of NiO(111) grown on Ni(111). The desorbing molecules we re detected state selectively via a resonance enhanced ionization tech nique [REMPI(1+1)] using the A (2) Sigma(upsilon'=0,1,2)<--X (2) Pi(up silon''=0,1,2) transition as intermediate state. Our results are compa red with our experiments on NO desorption from NiO(100). The similarit ies and differences of the results due to the different surface struct ure of the polar NiO(111) and the non polar NiO(100) are discussed. Fo r both surfaces we observe bimodal velocity flux distributions indepen dent of the rovibrational state. Due to a rotational temperature of ab out 400 K and a vibrational temperature of 1800 K thermal processes ca n be ruled out. The wavelength dependence of the desorption cross sect ion strongly correlates with the electronic structure of the NiO indic ating a surface mediated excitation process. The spin orientation in t he NO molecules influences the life time of the excited state dependin g on the magnetic property of the NiO surface.