Activation barriers for chemisorption of deuterium on aluminum cluster ions: Influence of oxygen preadsorption

Abstract

Activation barriers for chemisorption of deuterium on size-selected aluminum clusters with one or two preadsorbed oxygen atoms (Al n O k +, n=10–27, k=1, 2) are reported. These measurements were made by determining the collision energy threshold for chemisorption using low energy ion beam techniques. Oxygen preadsorption has a dramatic effect on the activation barriers for some of the smaller clusters ( n<18). For example, preadsorption of one oxygen atom on Al 15 + causes the activation barrier to increase by over 0.5 eV from that observed with the bare cluster. The origin of these very size-specific changes caused by oxygen preadsorption may be the result of a global perturbation of the cluster's electronic properties rather than involving a site-specific mechanism.