The theoretical expression for the probability of two-photon decay of helium in the 2 3 S 1 metastable level is derived. It is found that this expression is quite different from the corresponding expression for the 2 1 S 0 -> 1 1 S 0 transition. It is shown that the transition probability computed by Mathis in 1957 is overestimated by a very large amount and that A (2 3 S 1 -> 1 S 0 ) less, similar 10 -10 s -1 .

Journal of Physics B Atomic and Molecular PhysicsJul 1, 196813 citations

Lifetime measurement of He− using an electrostatic ion trap

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Optics and Spectroscopy

Difference between measured and theoretical values of the probability of spontaneous decay of a 3 3 P helium level

O. V. Oginets, Valerii B Smirnov, Yu. A. Tolmachev

Published Jul 1, 1977• 0 citations

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Alex Wolf, K. G. Bhushan, I. Ben-Itzhak +4 more

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

We have investigated the radiative decay of the metastable level

5d^{4}D_{7∕2}

{\mathrm{Xe}}^{+}

. Theoretically we find the decay to be heavily dominated by an

M2

transition and not by

M1∕E2

transitions. Lifetime measurements of

5d^{4}D_{7∕2}

in a storage ring are difficult since magnetic mixing of the metastable with a short-lived level quenches its population. Decay rates were determined at different magnetic field strengths

(B)

in order to allow a nonlinear extrapolation to

B=0

. The experimental lifetime of $2.4\ifmmode\pm\else\textpm\fi{}0.8\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ was in agreement with the calculated value, but much smaller than previously estimated.

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.