Dynamics of excited electronic states at clean and adsorbate-covered insulator surfaces

We present an ab initio approach to electronic excitations of surface systems and to their dynamics. Based on a density-functional calculation for the electronic ground state, excitations are described by many-body perturbation theory, taking electronic correlation effects and electron–hole interaction into account. This approach yields highly reliable results for electronic spectra, optical excitations, and excited-state total energies. In addition, the femtosecond dynamics (like, e.g., charge-transfer processes) of excited states can be evaluated. As examples, we discuss surface excitons at the LiF(0 0 1)-(1 × 1) surface, as well as the initial decay of the first excited state of CO molecules due to adsorption of the molecules on the insulator surface MgO(0 0 1)-(1 × 1).