Photodesorption of diatomic molecules from surfaces: A theoretical approach based on first principles

In the first part of this review, we will focus on scalar properties of desorbing diatomic molecules from insulating surfaces, where we also present a recently developed strategy of obtaining accurate potential energy surfaces using quantum chemical approaches. In general, diatomic molecules on large band gap materials such as oxide surfaces are studied which allows the use of sufficiently large cluster models and accurate ab initio methods beyond density functional theory (DFT). In the second part, we will focus on the vectorial aspects of the dynamics of nuclear motion and present simulations of experimentally accessible observables such as velocity distributions, Doppler profiles and alignment parameters. For each system, the microscopic mechanism of photodesorption is elucidated. We will demonstrate that the driving force of surface photochemistry is strongly dependent on details of the electronic structure of the adsorbate-substrate systems. This implies that great caution is advisable if experimental results are interpreted using empirical or semi-empirical models.