THE PHOTODISSOCIATION OF TERT-BUTYL NITRITE ADSORBED ON AG(111) - BIMODAL VELOCITY DISTRIBUTIONS OF THE PHOTOPRODUCTS

In this study the photodissociation of physisorbed tert-butyl nitrite, (CH3)(3)CONO, adsorbed on Ag(111) by 355 nm light is investigated at coverages between 0.15 and 50 layers at 85 K. Upon irradiation, time-o f-flight spectroscopy showed desorbing NO molecules due to the photodi ssociation of the tert-butyl nitrite. These molecules show a bimodal v elocity distribution with a thermal and a hyperthermal component at al l the investigated coverages. The yield and the velocity of the hypert hermal component saturated at a coverage of 5 layers. The conclusion i s made that if more than 5 layers are adsorbed the hyperthermal compon ent is produced in the top 5 layers of the film via a direct excitatio n mechanism. The thermal component consisted of NO photoproducts which had equilibrated to the substrate temperature. (C) 1997 Elsevier Scie nce B.V.