Effect of collision energy and incidence angle on the precursorhyphen;mediated dissociative chemisorption of N2on W(100)

摘要

The dissociative chemisorption of N2on W(100) is found to fall rapidly with increasing kinetic energyEiin the range 26 to 450 meV. For a surface temperatureTsof 300 K, the initial dissociative chemisorption probabilityS0falls from sim;0.8 atEi=26 meV to 0.15 at 450 meV. Over this range of energies the dissociation probability is also found to fall rapidly withTs, and to be relatively insensitive to surface coverage at lowTs, strongly suggesting that dissociation occurs in this system via a precursor under these conditions. This picture is supported by angular distribution measurements of the scattered molecules which are consistent with an appreciable cosine component, which also becomes smaller asEiincreases. Results are found to be surprisingly insensitive to the incidence angle over the range 0deg; to 70deg;, indicating that the trapping process scales quite closely with the total incidence energy.