Hot H photochemistry of H2S and CO coadsorbed on Cu(111) at 68 K

摘要

Photochemistry involving two types of molecules coadsorbed at monolayer coverage on a catalytically active single crystal metal surface at low temperatures has been observed with mass spectrometry and high resolution electron energy loss spectroscopy. Irradiation in the wavelength range 240ndash;365 nm of H2S and CO coadsorbed on Cu(111) at 68 K leads to the desorption of H2, CO, H2S, HCO, H2CO, and the formation of HCO, H2CO, and OCS on the surface. The primary step of the photoreaction involves the selective photodissociation of H2S, generating a hot H atom (significantly more energetic than in thermal equilibrium) and HS fragment in ground and excited vibrational states. Subsequent collisions with coadsorbed species give rise to the observed photoproducts. The wavelength dependence for CO and HCO formation generally follows that of the H2signal. The cross sections at 240 nm for photoinduced desorption of the two most abundant products, H2and CO, are 2.4 plusmn; 0.7 times; 10minus;20and 1.2 plusmn; 0.6 times; 10minus;20cm2, respectively.