A note on the vibrational efficacy in molecule-surface reactions

Abstract

The effectiveness of vibrational energy in promoting dissociation of molecules colliding with surfaces can be measured through the so-called vibrational efficacy. It is by many thought to be a pure "energetic" measure and therefore believed to be limited from below by zero (in the case that there is no increase in dissociation probability upon vibrational excitation) and from above by one (in the case that all of the vibrational excitation energy is used to promote reaction).However, the quantity vibrational efficacy is clearly linked to the detailed dynamics of the system, and straightforward considerations lead to the conclusion that it is not limited either from below or above. Here we discuss these considerations together with a quasi-classical dynamics study of a molecule-surface system, N 2 /Ru(0001), for which a vibrational efficacy bigger than one has been found both experimentally and theoretically. We show that an analysis of the vibrational efficacy only in terms of energy transfer from vibration to translation can be too simple to describe the behavior of systems for which the potential energy surfaces present (high) reaction barriers, potential corrugation and anisotropy, and curved reaction paths.

Dissociative dynamics of O2 on Ag(110)

“…Similar findings regarding the efficiency of the vibrational energy in dissociation has been reported for other late barrier systems. [42][43][44][45] As of here, the fact finding a vibrational efficacy greater than one simply shows that the average energy barriers encountered by the molecule are lower for the vibrationally excited molecule than for the ground state molecule, as it was nicely demonstrated by Díaz and Olsen. 44 In the following we analyze using classical calculations the dependence of S 0 (E i ) on the polar incidence angle.…”

Comparative dynamical study of the HD and isotopomers interacting with Pd(111) and Cu(110) surfaces

“…Dissociative adsorption of H 2 on Cu(1 1 0) is a direct process with late activation energy barriers [12] for which the adiabatic energy transfer from vibration to perpendicular motion that takes place in the entrance channel due to vibrational softening [19], plays an important role (see [20,3,21] and references therein). This effect is properly accounted for by QC calculations.…”

Nonmonotonic dissociative adsorption of vibrationally excitedH2on metal surfaces

“…Similar predictions have been reported from stateof-the-art quantum and classical 6D dynamical methods applied to vibrationally excited molecules. [29][30][31][32][33] But apart from this and in spite of the potentiality of this new generation of experiments, not much new insight on chemisorption or dissociative adsorption of vibrationally excited molecules has been achieved.…”