Generation of"bastard" molecular ionsfromvanderWaals clusters: Arn(C2Cl4)m+ ions, suspected interlopers in collection ofsolar neutrinos (molecular beam/supersonic expansion/mass spectroscopy)

ABSTRACT Gaseous molecular ions containing argon andperchlorethylene, Arn(CgCI4)m' inwhichn-1-29andm:- 1-4,areproducedbyelectronbombardmentofvanderWaalsclustersformedbyexpandinganAr/C2CI4mixture through asupersonicnozzle. Previous attemptstoobservesuchions in ahigh-pressuremassspectrometerwerenotsuccessful, aswithmanyother("bas-tard") ions that similarly lack a stable chemically boundneutralparentmolecule. This is probablydueto dissociation inducedbythe large exoergicity fromcharge transfer between species thatdiffergreatlyinionizationpotential. UseofvanderWaalsclustersasparentspeciesavoidsentirelytheexoergicityproblem.andthusoffersageneralmethodtogeneratebastardions. The Ar(C2C1)m+ ions have been suspected ofinterfering with collection of 'Ar' ionsproducedbythe37 Cl(ve)37Ar' reactioninthesolarneutrino observatory. Although,asshown by ourresults, theseionsaresta-ble, they are unlikely to inhibit collection on the longtime scaleofthe solar neutrinoexperiment.