Collision induced dissociation of diatomic molecules on surfaces: A charge transfer mechanism

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Abstract
A theory is presented which accounts for one of the possible mechanisms responsible for dissociativescattering of diatomic molecules from surfaces. If on the incident trajectory of the molecule, a surface‐to‐molecule electron transfer occurs and on the outgoing trajectory, the reverse, then the temporary negative molecular ion formed for the time duration between electron hops will displace in its intramolecular vibrational coordinate. The molecule will emerge as a vibrationally excited neutral, with some of the excited states lying within the dissociative continuum. A model is described for this process in which the center‐of‐mass translational motion is handled classically and the intramolecular motion via wave packet dynamics. The theory is energy and probability conserving and microscopically reversible. Dissociation probabilities calculated as a function of incident energy and system parameters are discussed in the light of experimental measurements for the system of I2dissociativelyscattered from MgO surfaces.