Theory of rate processes at metal surfaces. II. The role of substrate electronic excitations

A theoretical description of reactive molecular processes at metallic surfaces is formulated, following the Feschbach theory of nuclear reactions. Special attention is directed towards: (i) the role of substrate electron-hole pair excitations, both as a heat bath and as an entity permitting access to reaction channels not open in the absence of an excitation continuum; (ii) the importance of nuclear Franck–Condon factors; (iii) substrate induced quasiadiabatic electronic transitions on the incident atoms or molecules; and (iv) incorporation of substrate dynamic structure factors into the theory. Simple illustrative examples are presented which demonstrate the physical content of the formal theory and its relationship to various simplified models.