TRIMODAL VELOCITY DISTRIBUTIONS OF NITRIC-OXIDE FOR ULTRAVIOLET PHOTODISSOCIATION OF CH3ONO ADSORBED ON AG(111)

The photodissociation of less than or equal to 1.0 monolayer methyl ni trite adsorbed on Ag(111) has been studied by angle- and mass-resolved time-of-flight spectrometry. Irradiation with 248 or 351 nm photons l eads to ejection of NO with three translational energy components; the fast component is peaked away from the surface normal. The angular di stribution of the ejected NO depends on the initial coverage and photo lysis wavelength. A direct excitation mechanism is invoked for all thr ee components; the fast molecules are directly ejected, the intermedia te speed molecules have undergone one collision, and the slow molecule s have undergone several collisions. (C) 1998 Published by Elsevier Sc ience B.V. All rights reserved.