title: Detection of Negative Charge Carriers in Superfluid Helium Droplets: The Metastable Anions He*-and He2*-
abstract: Helium droplets provide the possibility to study phenomena at the very low temperatures at which quantum mechanical effects are more pronounced and fewer quantum states have significant occupation probabilities. Understanding the migration of either positive or negative charges in liquid helium is essential to comprehend charge-induced processes in molecular systems embedded in helium droplets. Here, we report the resonant formation of excited metastable atomic and molecular helium anions in superfluid helium droplets upon electron impact. Although the molecular anion is heliophobic and migrates toward the surface of the helium droplet, the excited metastable atomic helium anion is bound within the helium droplet and exhibits high mobility. The atomic anion is shown to be responsible for the formation of molecular dopant anions upon charge transfer and thus, we clarify the nature of the previously unidentified fast exotic negative charge carrier found in bulk liquid helium.
authors: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck , Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors: Andreas
authors: A
authors: Mauracher
authors: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck , Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors: Matthias
authors: M
authors: Daxner
authors: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck , Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors: Johannes
authors: J
authors: Postler
authors: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck , Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors: Stefan E
authors: SE
authors: Huber
authors: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck , Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors: Stephan
authors: S
authors: Denifl
authors: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck , Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors: Paul
authors: P
authors: Scheier
authors: Max Planck Institut für Dynamik und Selbstorganisation , Am Fassberg 17, D-37077 Göttingen, Germany.
authors: J Peter
authors: JP
authors: Toennies