Spectroscopic studies of rubidium vapour zone produced by thermal evaporation in noble gas

The time evolution of the extinction spectra of the rubidium vapour zone has been measured during the process of gas evaporation. The structure of the spectra and their time dependence show the occurrence of atoms, dimers, clusters and microcrystals. Also, they show a size trend in the surface plasma resonance frequency of rubidium clusters. Also, vapour species in each zone were selectively excited by using laser light and the emission spectra were measured. Some of the observed spectra were compared with theoretical ones, and information on the following points was derived: (1) the mechanism of rubidium cluster and microcrystal growth in the gas evaporation method, (2) the size trend of the collective mode resonance of the valence electrons, (3) the excitation energy transfer between rubidium vapour species, (4) the structure of the vapour zone and (5) the mechanism of laser photofragmentation of clusters.