Photophysics and Photochemistry of NO on Ag(111), Cu(111), and Si(111)7 × 7
We have performed photon induced desorption (PID) from NO adsorbed on Ag(111), Cu(111), and Si(111)7 × 7 at 85 K in the wavelength region 250–800 nm by using Xe and Hg-Xe arc lamps in combination with a monochromator (P≤30 mWcm—2). The adsorption of NO on these surfaces and subsequent changes after irradiation were characterized by high resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). On Ag(111), PID of NO and N2O have been observed from the NO saturated surface. On Cu(111), PID of both NO and N2O has also been observed. N2O is photosynthe-sized from photoinduced reactions. On Si(111)7 × 7, photon irradiation induces both desorption and dissociation of NO and photosynthesis of N2O. The N2O products partially desorb intact and partially dissociate into N2 and O, which leads to N2 desorption. PID of NO on Ag(111) and Cu(111) is state selective and occurs primarily for NO adsorbed in atop states. On Si(111)7 × 7, both atop and bridge bonded NO are photoactive. From the wavelength dependences of the PID, we suggest that the photoexcitation of the adsorbate (2πocc level) is the more important mechanism for Ag and Cu for photon energy≥3.4 eV; the substrate mediated process, however, is more dominant for Si.
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