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Physical Review Letters

Observation of the Molecular Helium Negative Ion He2−

Young K. Bae, M. J. Coggiola, James R. Peterson

Published Feb 27, 1984• 53 citations
Publisher

Abstract

Long-lived metastable ${\mathrm{He}}_{2}^{\ensuremath{-}}$ negative ions have been observed for the first time. They were produced from ${\mathrm{He}}_{2}^{+}$ by two-step electron capture in a Cs vapor target. The apparent autodetachment decay rates have been measured at several delay times after formation, and indicate the presence of more than one state, with the lifetime of the major component exceeding 100 \ensuremath{\mu}s. The most likely configurations are ${^{4}\ensuremath{\Sigma}_{g}}^{+}$ and/or $^{4}\ensuremath{\Pi}_{g}$ states bound below ${\mathrm{He}}_{2}({^{3}\ensuremath{\Sigma}_{g}}^{+})$.

DOI
10.1103/physrevlett.52.747

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The predicted metastable 4S3/2e^{4}\mathrm{S}_{3/2}^{\mathrm{e}}4S3/2e​ ${\mathrm{Ar}}^{\mathrm{\ensuremath{-}}}$ ion has been observed for the first time. It was produced from an Ar+{\mathrm{Ar}}^{+}Ar+ beam by two-step electron capture in Cs vapor. Decay-rate measurements favor the existence of only one state with a lifetime of 350\ifmmode\pm\else\textpm\fi{}150 ns.
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