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arXiv · 1611.06769

On Subthreshold Ionization of Helium Droplets, Ejection of He+, and the Role of Anions

Michael Renzler·Matthias Daxner·Nikolaus Weinberger·Stephan Denifl·Paul Scheier·Olof Echt
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Abstract

The mechanism of ionization of helium droplets has been investigated in numerous reports but one observation has not found a satisfactory explanation: How are $He^+$ ions formed and ejected from undoped droplets at electron energies below the ionization threshold of the free atom? Does this path exist at all? A measurement of the ion yields of $He^+$ and $He_2^+$ as a function of electron energy, electron emission current, and droplet size reveals that metastable $He^{*-}$ anions play a crucial role in the formation of free $He^+$ at subthreshold energies. The proposed model is testable.

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Michael Renzler, Matthias Daxner, Nikolaus Weinberger, Stephan Denifl, Paul Scheier, Olof Echt. 2016-11-21. On Subthreshold Ionization of Helium Droplets, Ejection of He+, and the Role of Anions. https://doi.org/10.1039/c4cp03236e

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