Physical Review A

Observation of the metastable negative beryllium ion, Be− ( Pe4 )

Young K. Bae, James R. Peterson

Published Oct 1, 1984• 48 citations

Abstract

The existence of the theoretically predicted $2s 2{p}^{2}^{4}P^{e}$ metastable ${\mathrm{Be}}^{\ensuremath{-}}$ ion has been confirmed by experiment. The autodetachment decay rates at several decay times after formation show the presence of more than one substate, with the lifetime of the longest component exceeding 100 \ensuremath{\mu}s.

DOI: 10.1103/physreva.30.2145

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Physical Review A

Observation of the metastable negative beryllium ion, Be− ( Pe4 )

Young K. Bae, James R. Peterson

Published Oct 1, 1984• 48 citations

Publisher

Abstract

The existence of the theoretically predicted

2s 2{p}^{2}^{4}P^{e}

metastable

{\mathrm{Be}}^{\ensuremath{-}}

ion has been confirmed by experiment. The autodetachment decay rates at several decay times after formation show the presence of more than one substate, with the lifetime of the longest component exceeding 100 \ensuremath{\mu}s.

DOI: 10.1103/physreva.30.2145

Related papers

Observation of the metastable negative argon ion Ar−

Young K. Bae, James R. Peterson, A. S. Schlachter +1 more

The predicted metastable $^{4}\mathrm{S}_{3/2}^{\mathrm{e}}$ ${\mathrm{Ar}}^{\mathrm{\ensuremath{-}}}$ ion has been observed for the first time. It was produced from an ${\mathrm{Ar}}^{+}$ 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.The predicted metastable $^{4}\mathrm{S}_{3/2}^{\mathrm{e}}$ ${\mathrm{Ar}}^{\mathrm{\ensuremath{-}}}$ ion has been observed for the first time. It was produced from an ${\mathrm{Ar}}^{+}$ 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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The lifetime of the metastable autodetaching 1s2s2p $^{4}$ ${\mathit{P}}_{5/2}$ level of the $^{4}\mathrm{He}^{\mathrm{\ensuremath{-}}}$ ion has been measured by a time-of-flight technique to be 350\ifmmode\pm\else\textpm\fi{}15 \ensuremath{\mu}s using a heavy-ion storage ring. Blackbody-induced photodetachment of this weakly bound level is shown to influence the decay rate by nearly 20%, an effect not discussed previously. The magnetic-field-induced mixing effects provide additional information about the lifetime of the close-lying $^{4}$ ${\mathit{P}}_{3/2}$ level, yielding \ensuremath{\tau} ${(}^{4}$ ${\mathit{P}}_{3/2}$ )=12\ifmmode\pm\else\textpm\fi{}2 \ensuremath{\mu}s. The observed lifetimes are consistent with previous experimental values, but the accuracy of the $^{4}$ ${\mathit{P}}_{5/2}$ lifetime is improved by a factor of 6, allowing a detailed test of theoretical predictions to be performed. The $^{4}$ ${\mathit{P}}_{5/2}$ lifetime is significantly shorter than most recent advanced theoretical results, but in agreement with a multiconfiguration Hartree-Fock approach accurately describing the initial bound $^{4}$ ${\mathit{P}}_{5/2}$ and the final continuum $^{2}$ ${\mathit{F}}_{5/2}$ states.The lifetime of the metastable autodetaching 1s2s2p $^{4}$${\mathit{P}}_{5/2}$ level of the $^{4}\mathrm{He}^{\mathrm{\ensuremath{-}}}$ ion has been measured by a time-of-flight technique to be 350\ifmmode\pm\else\textpm\fi{}15 \ensuremath{\mu}s using a heavy-ion storage ring. Blackbody-induced photodetachment of this weakly bound level is shown to influence the decay rate by nearly 20%, an effect not discussed previously. The magnetic-field-induced mixing effects provide additional information about the lifetime of the close-lying $^{4}$${\mathit{P}}_{3/2}$ level, yielding \ensuremath{\tau}${(}^{4}$${\mathit{P}}_{3/2}$)=12\ifmmode\pm\else\textpm\fi{}2 \ensuremath{\mu}s. The observed lifetimes are consistent with previous experimental values, but the accuracy of the $^{4}$${\mathit{P}}_{5/2}$ lifetime is improved by a factor of 6, allowing a detailed test of theoretical predictions to be performed. The $^{4}$${\mathit{P}}_{5/2}$ lifetime is significantly shorter than most recent advanced theoretical results, but in agreement with a multiconfiguration Hartree-Fock approach accurately describing the initial bound $^{4}$${\mathit{P}}_{5/2}$ and the final continuum $^{2}$${\mathit{F}}_{5/2}$ states.

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H. H. Andersen, T. Andersen, U. V. Pedersen

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The lifetimes of the metastable $1s2s2p{ }^{4}{P}_{5/2}$ level of ${\mathrm{He}}^{\ensuremath{-}},$ as well as the lifetime of the average of the ${}^{4}{P}_{3/2}$ and ${}^{4}{P}_{1/2}$ levels, have been measured using a new type of ion trap that stores keV ion beams using electrostatic fields only. The use of a pure electrostatic field avoids the complication of magnetic-field-induced mixing effects, which can interfere with the measurement of the spontaneous decay. The measured lifetime for the ${}^{4}{P}_{5/2}$ state, after correction for decay induced by blackbody radiation, is $343\ifmmode\pm\else\textpm\fi{}10 \ensuremath{\mu}\mathrm{s}.$ This value is consistent with previous experiments, and in excellent agreement with the most recent theoretical calculations. The average lifetime of the ${}^{4}{P}_{3/2}$ and ${}^{4}{P}_{1/2}$ is $8.9\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}\mathrm{s},$ which is about 20% lower than the weighted theoretical value.The lifetimes of the metastable $1s2s2p{ }^{4}{P}_{5/2}$ level of ${\mathrm{He}}^{\ensuremath{-}},$ as well as the lifetime of the average of the ${}^{4}{P}_{3/2}$ and ${}^{4}{P}_{1/2}$ levels, have been measured using a new type of ion trap that stores keV ion beams using electrostatic fields only. The use of a pure electrostatic field avoids the complication of magnetic-field-induced mixing effects, which can interfere with the measurement of the spontaneous decay. The measured lifetime for the ${}^{4}{P}_{5/2}$ state, after correction for decay induced by blackbody radiation, is $343\ifmmode\pm\else\textpm\fi{}10 \ensuremath{\mu}\mathrm{s}.$ This value is consistent with previous experiments, and in excellent agreement with the most recent theoretical calculations. The average lifetime of the ${}^{4}{P}_{3/2}$ and ${}^{4}{P}_{1/2}$ is $8.9\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}\mathrm{s},$ which is about 20% lower than the weighted theoretical value.

Physical Review AJan 1, 199956 citations

The existence of the theoretically predicted

2s 2{p}^{2}^{4}P^{e}

metastable

{\mathrm{Be}}^{\ensuremath{-}}

The predicted metastable

^{4}\mathrm{S}_{3/2}^{\mathrm{e}}

${\mathrm{Ar}}^{\mathrm{\ensuremath{-}}}$ ion has been observed for the first time. It was produced from an

{\mathrm{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.

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 ${\mathrm{He}}_{2}({^{3}\ensuremath{\Sigma}_{g}}^{+})$.

The lifetime of the metastable autodetaching 1s2s2p

^{4}

{\mathit{P}}_{5/2}

level of the $^{4}\mathrm{He}^{\mathrm{\ensuremath{-}}}$ ion has been measured by a time-of-flight technique to be 350\ifmmode\pm\else\textpm\fi{}15 \ensuremath{\mu}s using a heavy-ion storage ring. Blackbody-induced photodetachment of this weakly bound level is shown to influence the decay rate by nearly 20%, an effect not discussed previously. The magnetic-field-induced mixing effects provide additional information about the lifetime of the close-lying

^{4}

{\mathit{P}}_{3/2}

level, yielding \ensuremath{\tau}

{(}^{4}

{\mathit{P}}_{3/2}

)=12\ifmmode\pm\else\textpm\fi{}2 \ensuremath{\mu}s. The observed lifetimes are consistent with previous experimental values, but the accuracy of the

^{4}

{\mathit{P}}_{5/2}

lifetime is improved by a factor of 6, allowing a detailed test of theoretical predictions to be performed. The

^{4}

{\mathit{P}}_{5/2}

lifetime is significantly shorter than most recent advanced theoretical results, but in agreement with a multiconfiguration Hartree-Fock approach accurately describing the initial bound

^{4}

{\mathit{P}}_{5/2}

and the final continuum

^{2}

{\mathit{F}}_{5/2}

states.

The lifetimes of the metastable

1s2s2p{ }^{4}{P}_{5/2}

level of ${\mathrm{He}}^{\ensuremath{-}},$ as well as the lifetime of the average of the

{}^{4}{P}_{3/2}

and

{}^{4}{P}_{1/2}

levels, have been measured using a new type of ion trap that stores keV ion beams using electrostatic fields only. The use of a pure electrostatic field avoids the complication of magnetic-field-induced mixing effects, which can interfere with the measurement of the spontaneous decay. The measured lifetime for the

{}^{4}{P}_{5/2}

state, after correction for decay induced by blackbody radiation, is $343\ifmmode\pm\else\textpm\fi{}10 \ensuremath{\mu}\mathrm{s}.$ This value is consistent with previous experiments, and in excellent agreement with the most recent theoretical calculations. The average lifetime of the

{}^{4}{P}_{3/2}

and

{}^{4}{P}_{1/2}

is $8.9\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}\mathrm{s},$ which is about 20% lower than the weighted theoretical value.