Reactive and inelastic scattering dynamics of hyperthermal oxygen atoms on a saturated hydrocarbon surface

Abstract

Articles you may be interested inQuantum dynamical treatment of inelastic scattering of atoms at a surface at finite temperature: The random phase thermal wave function approach Erratum: "Comparative dynamics of Cl ( 2 P) and O ( 3 P) interactions with a hydrocarbon surface" [J. Chem. Eley-Rideal reactions between H atoms on metal and graphite surfaces: The variation of reactivity with substrateThe dynamics of the initial interactions of hyperthermal O atoms with a saturated hydrocarbon surface have been investigated by directing an O-atom beam at a continuously refreshed liquid squalane surface and monitoring time-of-flight and angular distributions of inelastically scattered O atoms and reactively scattered OH and H 2 O. These products are formed through thermal and nonthermal processes. The inelastic scattering processes may be described in terms of the limiting cases of direct inelastic scattering ͑nonthermal͒ and trapping desorption ͑thermal͒. The initial step leading to production of volatile OH and H 2 O is believed to be direct H-atom abstraction to form OH. Once formed, the OH may scatter directly into the gas phase before thermal equilibrium with the surface is reached, or it may undergo further collisions and reactions with the surface. These secondary interactions include trapping and desorption of OH and abstraction of a second hydrogen atom to form H 2 O. Interactions that occur before thermal equilibrium with the surface can be reached lead to products that exit the surface at hyperthermal velocities, while those that occur in thermal equilibrium with the surface yield products that leave the surface at thermal velocities given by the surface temperature. Direct, single-collision scattering events that produce O and OH are described with a kinematic picture that allows the determination of the effective surface mass encountered by an incident O atom, the atom-surface collision energy in the center-of-mass frame, and the fraction of the center-of-mass collision energy that goes into translation of the scattered gaseous product and the recoiling surface fragment. Center-of-mass velocity-flux maps for OH indicate either single-collision events through a largely collinear O-H-C transition state or multiple-collision events in which initially formed OH scatters inelastically from the surface.

Dynamics of the Reaction of O(3P) Atoms with Alkylthiol Self-assembled Monolayers

“…The true absolute reactivity of the O( 3 P) with an alkyl SAM is, of course, unknown. However, it is likely, on the basis either of related measurements on liquid surfaces where inelastic scattering is known to be the major channel 58,60 or a priori arguments based on gas-phase activation energies and Arrhenius factors, 79,80 to be much less than unity. We therefore believe this is not the practical limiting factor on the useful lifetime of the SAMs under our conditions.…”

“…As in our previous work, 44 we select these to mimic the known distributions in the molecular beam scattering experiments of Minton and coworkers on O( 3 P) with squalane. [58][59][60][61] For either TD or IS, if the OH trajectory traverses the probe laser beam volume it makes a contribution to the signal during the time that it is present. We accumulate these suitably weighted contributions for a sufficiently large number of trajectories to achieve satisfactory statistics on the predicted profiles.…”

“…This reproduced the more highly resolved bimodal velocity and angular distributions obtained earlier by Minton and co-workers. [58][59][60][61] They used complementary molecular-beam scattering methods that were an evolution of Nathanson's approach to inelastic scattering. 27,28 With the added state-selectivity of LIF detection, we have been able to extract internal state distributions for both of these components.…”

Crossed-Beams and Theoretical Studies of Hyperthermal Reactions of O(3P) with HCl

“…[38][39][40] Details about the experimental apparatus can be found in an earlier paper. 41 In general, a pulsed, hyperthermal beam of oxygen atoms was crossed at right angles with a pulsed, supersonic beam of HCl (or DCl) gas (Matheson, 99.995%).…”

Determining the composition of the vacuum–liquid interface in ionic-liquid mixtures

“…Signal sizes were referenced against interleaved measurements of the well-studied standard, squalane. [32][33][34][35][36][37][38][39][40] To achieve the desired precision, the appearance profiles were averaged over typically ten sets of independent measurements over several different days for each mixture studied. They were corrected for a small background signal caused by a HONO impurity in the chamber by the procedure described previously.…”