INTERACTION OF ULTRAVIOLET PHOTONS WITH NO NI(111)/

The properties of the NO/Ni(111) system under exposure to ultraviolet photons of three different energies (6.4, 5.0, and 3.5 eV) generated b y nanosecond pulsed excimer laser, have been studied by ref-lection-ab sorption infrared spectroscopy and thermal desorption spectroscopy. It was found that the photoinduced process depends on the adsorbed tempe rature of NO on Ni(111). In adsorption at 80 K for submonolayer NO cov erage the dominant laser light-induced effect is dissociation of NO mo lecules, whereas for saturation coverage UV photons do not change the properties of the system. However, when a saturated layer is formed at a substrate temperature of 300 K, laser irradiation causes dramatic c hanges of RAIR spectra which can be attributed to the chemical changes in NO/Ni(111). Different photoinduced behaviors at 80 and 300 K origi nate from the different initial states of NO/Ni(111) formed at differe nt substrate temperatures. The photoinduced process is essentially the same for all photon energies used, although the cross section becomes lower as the photon energy decreases.