Quantum theory of reactive scattering and adsorption at surfaces

The interaction of atoms and molecule with surfaces is of great technological relevance. For a reliable theoretical description of the interaction dynamics of light atoms and molecules such as hydrogen or helium with surfaces, quantum effects have to be taken into account. In this article, I will discuss quantum effects in the interaction dynamics of both the substrate as well as the incident particles. There are pure quantum phenomenon such as elastic scattering and diffraction. Elastic scattering, i.e. scattering without any energy transfer to the substrate, is a consequence of the quantum nature of the substrate vibrations, the phonons. It is particularly important in the trapping of noble gas atoms at surfaces. In the case of elastic scattering at a periodic surface, the momentum parallel to the surface is conserved within multiples of the reciprical lattice vectors. This leads to diffraction, i.e. to a characteristic pattern of well-resolved scattering peaks. Further quantum effects that influence the scattering and reaction probabilities are threshold effects due to the opening up of new scattering channels, scattering resonances, tunneling, zero-point vibrations and quantization effects at transition states. These quantum will be discussed using the adsorption of rare gas atoms and the scattering and dissociative adsorption of hydrogen as examples.