Nonadiabatic charge transfer processes of oxygen on metal surfaces

Abstract

The dynamics of charge transfer processes of oxygen on metal surfaces is reviewed. Two theoretical frameworks, the adiabatic and the nonadiabatic, are compared with experiment. The O2/Al system is chosen as a representative example. In the adiabatic approach there is no barrier to dissociation. This fact contradicts experimental observations of an increase of the dissociation probability with incident energy. In this study a nonadiabatic framework is formulated where the encounter takes place simultaneously on four electronic surfaces, each representing a different charged oxygen species. The dynamics, starting from an oxygen molecule in the gas phase, is followed by solving the multichannel time dependent Schrödinger equation. The transition from the diabatic to the adiabatic limit is explored by varying the nonadiabatic coupling terms. By so doing the dissociation probability dependence on incident energy changes from a strong monotonic increase in the diabatic case, to a flat dependence in the adiabatic case. The influence of electronic quenching is also studied, based on a numerical solution of the Liouville von Neumann equation. The dynamics subject to quenching shows a stronger initial dependence on incident kinetic energy leading to saturation. The general trend is quite similar to the dynamics without quenching.

Role of Vibrationally Excited NO in Promoting Electron Emission When Colliding with a Metal Surface: A Nonadiabatic Dynamic Model

“…In the present case of a surface with a low work function, the crossing seam is almost parallel to the vibration and extends far out into high z values. In agreement with the results of Li and Guo and with calculations on the influence of dissipation on the charge transfer reactions of O 2 on metals, dissipation due to electron−hole pairs does not alter the qualitative features of the crossing dynamics which takes place predominantly near the crossing seam.…”

“…In the region of small coupling, relevant for this study, the total transition probability from one surface to the other is proportional to A ab 2 ; this means that the value of A ab could be fit to the total electron emission yield. 10,29 The quantum dynamics of the encounter was simulated by solving the multichannel time-dependent Shcro ¨dinger equation. 10 The initial wave function was constructed as a product of a plane wave describing the motion of NO toward the surface and a vibrational eigenstate.…”

“…The value of A ab was set as A ab = 0.45 eV for all the nonadiabatic coupling terms. In the region of small coupling, relevant for this study, the total transition probability from one surface to the other is proportional to ; this means that the value of A ab could be fit to the total electron emission yield. , The quantum dynamics of the encounter was simulated by solving the multichannel time-dependent Shcrödinger equation …”

Dissociative dynamics of O2 on Ag(110)

“…This discrepancy cannot be resolved by invoking non-adiabatic effects as was done to explain the dissociative adsorption of O 2 onto aluminium surfaces. 47,48 These effects generate energy barriers to dissociation in the entrance channel that would in general further reduce the calculated sticking probability as compared to our adiabatic results, worsening, instead of improving, the comparison with the experimental data.…”

Quantum Dynamical Approach to Ultrafast Molecular Desorption from Surfaces

“…An example is O 2 /Pt(111) . Similar models were developed for other systems and processes (e.g., molecule−surface scattering), for example, for O 2 /Al(111), , and NO/Cs/Ru . In these models, more than one degree of freedom was considered, for example, r , the interatomic distance within the diatomic molecule, and Z , the desorption coordinate.…”