Quantum Theory of Photodesorption of Neutrals from Metals: Ab Initio Calculations and Active Control

In continuation of previous work, two aspects of the ultraviolet laser‐induced desorption of NO from Pt (111) and ammonia from Cu(111) are investigated using different, quantum mechanical tools. First, for NO/Pt(111) it is shown with the help of simple, ab initio electronic structure cluster calculations, that previously introduced phenomenological two‐ and multiple‐state models are consistent with the more refined quantum chemical picture. Within this picture, the finite lifetime of a resonance state (“quenching”) is microscopically a consequence of the non‐adiabatic coupling of the resonance state to the metal electronic excitations. Further, both for NO/Pt(111) and ammonia/Cu(111) the possibility to actively control the desorption yields is investigated. For this purpose, time‐dependent wave packet propagations based on the nuclear Schrödinger equation are used. The proposed control mechanisms are (i) thermal and (ii) optical preparation of vibrational states of the adsorbate/substrate complex. The latter strategy, which is also supported by IR transition probabilities, is found to be much more efficient.