• Open Access

Solvation of Na+, K+, and Their Dimers in Helium

Authors

  • Lukas An der Lan,

    1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
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  • Peter Bartl,

    1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
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  • Christian Leidlmair,

    1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
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  • Roland Jochum,

    1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
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  • Dr. Stephan Denifl,

    1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
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  • Prof. Dr. Olof Echt,

    Corresponding author
    1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
    2. Department of Physics, University of New Hampshire, Durham, NH 03824 (USA)
    • Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
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  • Prof. Dr. Paul Scheier

    Corresponding author
    1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
    • Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria), Fax: (+43) 512-507-2932
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Abstract

Helium atoms bind strongly to alkali cations which, when embedded in liquid helium, form so-called snowballs. Calculations suggest that helium atoms in the first solvation layer of these snowballs form rigid structures and that their number (n) is well defined, especially for the lighter alkalis. However, experiments have so far failed to accurately determine values of n. We present high-resolution mass spectra of Na+Hen, K+Hen, Na2+Hen and K2+Hen, formed by electron ionization of doped helium droplets; the data allow for a critical comparison with several theoretical studies. For sodium and potassium monomers the spectra indicate that the value of n is slightly smaller than calculated. Na2+Hen displays two distinct anomalies at n=2 and n=6, in agreement with theory; dissociation energies derived from experiment closely track theoretical values. K2+Hen distributions are fairly featureless, which also agrees with predictions.

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