Radiative decay of laser excited clusters in molecular beams

Clusters are particles composed of a small number of atoms. They have extreme size- and composition dependent properties due to quantum confinement and electron correlation effects. The production of size selected clusters in macroscopic amounts, so that species can be used in applications, is determined by the system’s stability. For many years, the stability of clusters has been investigated by studying their fragmentation following laser excitation, and assuming that radiative decay is negligible. Recent experiments, however, have shown that this assumption is incorrect for several types of clusters and that current understanding of the phenomenon of photon emission from small excited clusters is poor. In this research, the radiative decay of laser-excited clusters will be investigated by addressing four key questions:

1. Is electron delocalization a determining factor in the radiative decay process of metallic clusters?
2. Is radiation altered if the composition of a cluster is modified?
3. Which decay mechanisms dominate at longer time scales?
4. What are the wavelength of the emitted photons?

To address them, clusters of different sizes and compositions will be laser-excited and their decay products investigated on time scales ranging from times as short as a microsecond up to several seconds. In combination with statistical modelling and ab initio quantum calculations, these experiments will provide a deeper understanding about the decay processes of excited clusters.