Molecular Beams and Cluster Nucleation

Abstract

For people working with molecular beams, the appearance of clusters due to condensation effects is detrimental since it limits the low temperature and high intensity regimes attainable with supersonic nozzle beams. Many studies have been devoted to the characterization of condensation processes in order to avoid cluster formation. On the other hand, if one is interested in the clusters themselves, molecular beams are a very rich area for the characterization of their fundamental properties [2.1,2.2]. There are several basic reasons to use molecular beams for the production and investigation of clusters: primarily the control on temperature and pressure of the gas forming the beam can produce the conditions of an efficient condensation. Moreover, clusters in molecular beams can be studied without the interference of matrices and/or substrates; their kinetic energy, in the eV range, is very interesting for a wealth of physico-chemical phenomena; their mass distribution can be controlled and they can be mass selected.