title: Sequential penning ionization: harvesting energy with ions.
abstract: We report the observation of the ejection of electrons caused by collisions of excited atoms with ions, rather than neutrals, leading to the production of doubly charged ions. Doping superfluid He droplets with methyl iodide and exposing them to electrons enhances the formation of doubly charged iodine atoms at the threshold for the production of two metastable He atoms. These observations point toward a novel ionization process where doubly charged ions are produced by sequential Penning ionization. In some cases, depending on the neutral target, the process also leads to a subsequent Coulomb explosion of the dopant.
authors.affiliation: Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Harald
authors.initials: H
authors.lastname: Schöbel
authors.forename: Peter
authors.initials: P
authors.lastname: Bartl
authors.forename: Christian
authors.initials: C
authors.lastname: Leidlmair
authors.forename: Matthias
authors.initials: M
authors.lastname: Daxner
authors.forename: Samuel
authors.initials: S
authors.lastname: Zöttl
authors.forename: Stephan
authors.initials: S
authors.lastname: Denifl
authors.forename: Tilmann D
authors.initials: TD
authors.lastname: Märk
authors.forename: Paul
authors.initials: P
authors.lastname: Scheier
authors.forename: Daniel
authors.initials: D
authors.lastname: Spångberg
authors.forename: Andreas
authors.initials: A
authors.lastname: Mauracher
authors.forename: Diethard K
authors.initials: DK
authors.lastname: Bohme