OPTICAL-PROPERTIES AND ELECTRONIC EXCITATIONS OF RARE-GAS CLUSTERS

The electronic structure of rare gas clusters has been probed with time- and spectrally resolved fluorescence methods. The character of different electronic excitations of pure (Ar, Kr, Xe) and doped (XeAr(n)) clusters containing up to 10(5) atoms is discussed and investigated as a function of the cluster size. Surface, bulk, Rydberg-and cluster-type excitations are responsible for absorption bands below the ionisation limit. A very important parameter within this context is the ratio of the cluster-radius and the radius of the electronic excitation. Modified solid state concepts are very suitable for the description of the unrelaxed excitations of the clusters. The interpretation of the decay and relaxation processes requires a molecular approach. Clusters containing a few hundred atoms show cluster specific excitations, which up to now cannot be explained within these two traditional concepts.