title: Cationic complexes of hydrogen with helium.
abstract: High-resolution mass spectra of helium nanodroplets doped with hydrogen or deuterium reveal that copious amounts of helium can be bound to H(+), H(2)(+), H(3)(+), and larger hydrogen-cluster ions. All conceivable He(n)H(x)(+) stoichiometries are identified if their mass is below the limit of ≈120 u set by the resolution of the spectrometer. Anomalies in the ion yields of He(n)H(x)(+) for x=1, 2, or 3, and n≤30 reveal particularly stable cluster ions. Our results for He(n)H(1)(+) are consistent with conclusions drawn from previous experimental and theoretical studies which were limited to smaller cluster ions. The He(n)H(3)(+) series exhibits a pronounced anomaly at n=12 which was outside the reliable range of earlier experiments. Contrary to findings reported for other diatomic dopant molecules, the monomer ion (i.e. H(2)(+)) retains helium with much greater efficiency than hydrogen-cluster ions.
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Bartl
authors.forename: Christian
authors.initials: C
authors.lastname: Leidlmair
authors.forename: Stephan
authors.initials: S
authors.lastname: Denifl
authors.forename: Paul
authors.initials: P
authors.lastname: Scheier
authors.forename: Olof
authors.initials: O
authors.lastname: Echt