VIBRATIONALLY EXCITED PRODUCTS AFTER THE PHOTODESORPTION OF NO FROM PT(111) - A TWO-MODE OPEN-SYSTEM DENSITY MATRIX APPROACH

摘要

The experimentally observed vibrational excitation of NO molecules photodesorbing from a Pt(111) surface is investigated numerically with the help of open-system density matrix theory. We extend Gadzuk's jumping wave packet model to treat DIET processes (desorption induced by electronic transitions, single-excitation limit) which is equivalent to a one-channel open system Liouville-von Neumann equation with coordinate-independent quenching, to cases when the electronic relaxation becomes coordinate-dependent. This allows for a more realistic but still economic and, hence, systematic study of DIET within a two-state, two-degrees of freedom model. Adopting ''reasonable'' Antoniewicz-type model potentials, we find that the experimental observations can semiquantitatively be rationalized if an electronic quenching rate decreasing with increasing N-O separation, is assumed. Preliminary two-mode DIMET simulations (desorption induced by multiple electronic transitions, multiple-excitation limit) within a stochastic wave packet approach are also presented. [References: 20]