The sticking of Osub 2 on a Pt(111) surface
J. Chem. Phys., 89 (7):
4381-4395 (1988)DOI: 10.1063/1.454824
Abstract
This paper reports detailed molecular beam measurements of the sticking
coefficient at zero coverage for O2 on a Pt(111) surface as a function
of initial energy (Ei), angle of incidence (thetai), and surface
temperature (Ts). Under most conditions the sticking coefficient
measures the probability for dissociative chemisorption. These results
demonstrate that both precursor mediated and quasi-direct dissociation
can be observed, depending upon the initial conditions. The quasi-direct
process is revealed by a step increase in the sticking with Ei. This
feature scales intermediately between Ei and the normal component
En, and is weakly dependent on Ts. The precursor mediated sticking
is well described by standard precursor kinetic models. At low Ei
and Ts, sticking measures trapping into a molecularly adsorbed state.
This trapping decreases more rapidly with Ei than anticipated from
simple models and scales intermediately between Ei and En. The sticking
results are discussed in terms of likely dynamic processes occurring
on a potential energy surface which contains an intermediate molecularly
adsorbed species formed by charge transfer from the metal to the
O2.