RESONANCE INTERFERENCE IN A 3-LEVEL SYSTEM WITH DYNAMIC COUPLING OF THE INTERMEDIATE STATE TO A VIBRATIONAL-MODE

Coherent electronic transitions are analysed in a three-level system w here the intermediate level is strongly coupled to a classical nuclear mode the dynamics of which is explicitly incorporated. Such a configu ration is representative of scanning tunnelling microscopy through a m olecular adsorbate. Solution of the equations of motion gives a drop i n the overall transition probability per unit time (current) from the initial to the final state when these two states are in resonance. Thi s observation differs from resonance effects obtained by second-order perturbation theory in stationary nuclear environments, and is associa ted with the motion of the intermediate state level through the resona nce region.