Femtosecond Spectroscopy on mass-selected Clusters

In general, clusters are a conglomeration of several monomeres, i.e. usually two to some thousand atoms or molecules. Therefore, clusters being neither atom nor bulk reveal properties that may differ significantly from those of the two limiting cases, depending strongly on the number of involved atoms (or molecules).In metal clusters, the delocalized conduction electrons are quantized in descrete levels due to the confinement. Therefore, such particles more likely behave like atoms or semiconductors.Using Time-Resolved Photoelectron Spectroscopy the relaxation of an excited state can be monitored. The cluster is initially excited by a first laser pulse and then probed by a second. With a time resolution of 100 femtoseconds very fast dynamics can be resolved. As an example, Ag clusters exhibit semiconductor-like properties rather than metallic