ADSORPTION AND PHOTOREACTIONS OF NO ON NB(110) AT 20-K

The adsorption and photon induced reactions in the wavelength region 240-610 nm of NO adsorbed on Nb(110) at 20 K has been studied by means of HREELS (DELTA-E1/2 less-than-or-equal-to 4 meV). The photoexperiments have been performed by using a Hg arc lamp in combination with various colour glass filters. At low exposure (less-than-or-equal-to 2 L) NO is adsorbed in part dissociatively and in part molecularly in several adsorption states. At higher exposure NO is also physisorbed. In addition the formation and adsorption of the ON-NO dimer has been observed. Simultaneously N2O is formed and adsorbed in small amount. No photon induced reactions have been observed above lambda > 375 nm. Below lambda < 340 nm the following photon stimulated phenomena have been found: (1) The (NO)2 dimer and the physisorbed NO molecules are desorbed from the surface. (2) NO and (NO)2 are photodissociated and atomic oxygen is adsorbed on the surface, simultaneously N2O is formed and adsorbed on the surface.