The European Physical Journal D

, Volume 43, Issue 1–3, pp 117–120 | Cite as

Electron impact ionization of thymine clusters embedded in superfluid helium droplets

  • F. ZappaEmail author
  • S. Denifl
  • I. Mähr
  • J. Lecointre
  • F. Rondino
  • Olof Echt
  • T. D. Märk
  • P. Scheier
Helium Clusters and Spectroscopy


Embedding molecules in helium clusters has become a powerful technique for the preparation of cold targets for spectroscopy experiments, as well as for the assembly of complex, fragile molecular species. We have recently developed a helium cluster source and a pick-up cell to produce neutral beams of doped helium droplets, to be used as targets in studies on electron collisions with molecules of biological relevance. In the present work we present the results of a series of experiments on electron-impact ionization of helium clusters doped with thymine and 1-methylthymine, where several interesting phenomena were observed, i.e., (i) electron impact ionization of molecular clusters inside the helium droplets leads predominantly to protonated clusters; (ii) the appearance energies are close to the ionization threshold of the helium atom but ionization efficiency curves in addition extend down by several eV; (iii) ionized molecular clusters can undergo metastable decay via the loss of one neutral monomer.


34.80.Gs Molecular excitation and ionization by electron impact 36.40.Qv Stability and fragmentation of clusters 82.33.Fg Reactions in clusters 87.50.Gi Ionizing radiations 


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Copyright information

© EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007

Authors and Affiliations

  • F. Zappa
    • 1
    Email author
  • S. Denifl
    • 1
  • I. Mähr
    • 1
  • J. Lecointre
    • 2
  • F. Rondino
    • 3
  • Olof Echt
    • 4
  • T. D. Märk
    • 1
  • P. Scheier
    • 1
  1. 1.Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität Innsbruck and Center of Molecular Biosciences InnsbruckInnsbruckAustria
  2. 2.Université Catholique de LouvainLouvain-la-NeuveBelgium
  3. 3.Facoltà di Farmacia, Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente AttiveUniversità “La Sapienza”RomeItaly
  4. 4.University of New HampshireDurhamUSA

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