EPR spectroscopy on single crystal surfaces
The group runs a unique research program, which uses cw-EPR spectroscopy under ultrahigh vacuum conditions to study paramagnetic centers on single crystalline surfaces. The group has developed this methodology over the last years and was able to show that it can be applied to a variety of systems ranging from isolated paramagnetic metal atoms to ferromagnetic metal particles. For such systems the analysis of the magnetic parameters allows to extract structural as well as electronic properties of the species under investigation, which are otherwise difficult to obtain with typical surface science methodology. It is also possible to investigate molecular species (radicals). These can be reaction intermediates (e.g. methyl radicals) or stable molecules. To this end it is also possible to elucidate the rotational dynamics of paramagnetic adsorbates given that they are stable against reactions.
In last years the group was mainly involved in the characterization of paramagnetic defects on oxides in particular on the MgO(001) surface and the impact these centers have on the chemistry of the surface. This is also the topic of a current project within the framework of the Cluster of Excellence UNICAT in which the activation of small molecules (oxygen, CO2, methane) is studied. Within the current project the group is engaged in a collaborative project involving the characterization of the paramagnetic defects in MgO as well as the activation of CO2 on Cr2O3 surfaces.