Resonance-mediated dissociative adsorption of hydrogen

Selective adsorption has been examined theoretically using time-dependent quantum-mechanical methods. In the simple case of a potential with no open channel to dissociation, we find that the description in terms of bound states of the laterally averaged potential holds, and perturbation theory gives adequate results for the lifetimes of the states. A more complicated situation, in which dissociation and resonance interact strongly, is beyond the reach of perturbation theory. Nevertheless, the resonances still exist at energies determined by kinematics. They decay more rapidly than before into both the dissociation and scattering channels. The most striking feature of the results is that the dissociation probability, as well as the diffraction intensities, exhibits a Fano profile around the resonance. Thus resonance diminished dissociation can be seen. We examine the possible inclusion of inelastic effects in our calculations, and the direct comparison with experiment this would allow.