Core Electron Excitations and Decay in Molecules

Using CO in its free form, coordinated to a metal atom, or adsorbed onto a surface as an example, some recent experiments are reviewed investigating secondary processes following the excitation of a core electron. These experiments deal with the electronic decay of a core hole excited state or the decay of the parent molecule into ionic fragments. The study of these secondary processes yields new insight into the formation of the molecular bond, static charge distributions, and dynamic charge transfer processes. These experiments also allow us to study energy redistribution in highly excited electronic states on a timescale equivalent to the lifetime of the core hole (10-14 sec).