CLUSTER ION FORMATION IN FREE JET EXPANSION PROCESSES AT LOW-TEMPERATURES

An experimental high voltage post-acceleration facility for the detection of high molecular weight cluster ions is described. A summary of results obtained with this facility in studies of high molecular weight water and argon cluster ions is presented. Results on studies of hydrogen cluster ion formation in the expansion of pure weakly ionized hydrogen gas are also presented. Attempts to limit cluster ion formation in hydrogen to quasi equilibrium conditions inside the ion source with source apertures as small as 0. 00125 cm were inconclusive. These studies indicate that approximately 25-33 cluster-ion hydrogen molecule collisions could serve to stabilize the growing cluster ions.