Comparative studies of cluster dynamics in the gas and condensed phases

Although an overview of the field of cluster dynamics is impossible to give in this Introductory Lecture, several important themes have emerged that can provide a backdrop for this Faraday Discussion. As a result, the first part of this paper introduces some of these themes, using results from the literature to illustrate some of the important issues. Although much of the work on clusters is being carried out in the gas phase (usually in free jet expansions and molecular beams), new approaches have recently been developed that permit the study of the same complexes in or on nanoscale clusters. In particular, recent developments in the field of superfluid helium droplet spectroscopy (SHEDS) permit high-resolution studies of atoms, molecules and clusters in this exotic quantum fluid. After introducing this new field, the author will discuss experiments from his own laboratory to illustrate some of the capabilities of the technique.