Hydrocarbon clusters from a foil diffusion source

Rydberg states and clusters of Rydberg states have been reported in several cases from high temperature sources, so-called diffusion sources. The present study uses the same technique as the one used for the study of excited Cs clusters (Åmanet al., 1990), and is aimed at highly excited Rydberg cluster formation from hydrogen containing molecules. Ionized clusters from a diffusion source with the graphite foil emitter at 1400 K are studied by time-of-flight mass spectrometry. The excited clusters are shown to be ionized by field ionization. The best results are found using ethylene in the source, and the flux from the source probably contains both hydrogen and hydrocarbon species. Typical clusters have a mass of 10,000–200,000 a.u., assuming singly charged clusters. The formation and stabilization (cooling) of such large clusters under the present conditions is only possible since excited states can form a condensed phase, of so called Rydberg matter (Manykinet al., 1981, 1982, Petterssonet al., 1992, Svenssonet al., 1991, 1992). The importance of excited hydrogen containing clusters for the chemistry and physics of interstellar space is pointed out.