Helium anion formation inside helium droplets

  • Elias Jabbour Al Maalouf
  • Julia Reitshammer
  • Anita Ribar
  • Paul Scheier
  • Stephan DeniflEmail author
Open Access
Regular Article
Part of the following topical collections:
  1. Topical Issue: Advances in Positron and Electron Scattering


The formation of He∗− is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗− inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15–70 nA) a quadratic dependence of the He∗− ion yield on the electron current is observed.

Graphical abstract


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© The Author(s) 2016

Open Access This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  • Elias Jabbour Al Maalouf
    • 1
  • Julia Reitshammer
    • 1
  • Anita Ribar
    • 1
  • Paul Scheier
    • 1
  • Stephan Denifl
    • 1
    Email author
  1. 1.Institut für Ionenphysik und Angewandte Physik, Universität InnsbruckInnsbruckAustria

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