THEORY OF DESORPTION INDUCED BY ELECTRONIC-TRANSITIONS - A TIME-INDEPENDENT QUANTUM-MECHANICAL APPROACH

A new method is developed for study of photon- or electron-stimulated desorption from noninsulator surfaces. Concise and physically transpar ent, closed form expressions for the observables in a desorption exper iment are given in terms of matrix elements of the interaction in stat ionary bases. The method is nonperturbative and spans the limits of we ak to strong substrate-adsorbate interactions. We propose the possibil ity of relaxing several approximations frequently adopted in theoretic al studies of desorption induced by electronic transitions. In particu lar, continuous decay of the transient electronic excitation produced by hot substrate carriers and the possibility of multiple electronic t ransitions follow naturally from the formulation and need not be intro duced ad hoc. The description of time-delayed desorption, resulting fr om occurrence of predesorption resonances, entails neither conceptual nor computational difficulty and vibrational relaxation is consistentl y accounted for. The method is tested by application to an empirical m odel of the NH3/Cu photodesorption dynamics. (C) 1997 American Institu te of Physics.