Radiative Lifetime of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>2</mml:mn><mml:mi> </mml:mi><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>S</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow /><mml:mrow /><mml:mrow /><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>Metastable State of Helium

Dyck, Robert S. Van; Johnson, C. E.; Shugart, Howard A.

doi:10.1103/physreva.4.1327

Cited by 97 publications

(24 citation statements)

References 19 publications

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“…At times longer than 10 −7 s all singlet-state excimers and excited atoms (except, perhaps, for the first excited state He(2 1 S), which in vacuum has a lifetime of 19 ms [38]), will have long decayed. Any photons produced at a later time must result from triplet states.…”

Section: Temperature and Electric Field Dependence Of Afterpulse Smentioning

confidence: 99%

Effect of an electric field on superfluid helium scintillation produced byα-particle sources

et al. 2012

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We report a study of the intensity and time dependence of scintillation produced by weak α-particle sources in superfluid helium in the presence of an electric field (0-45 kV/cm) in the temperature range of 0.2 to 1.1 K at the saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reduction in intensity with the application of an electric field. The reduction in the intensity of the prompt component is well approximated by a linear dependence on the electric field strength with a reduction of 15% at 45 kV/cm. When analyzed using the Kramers theory of columnar recombination, this electric field dependence leads to the conclusion that roughly 40% of the scintillation results from species formed from atoms originally promoted to excited states and 60% from excimers created by ionization and subsequent recombination with the charges initially having a cylindrical Gaussian distribution about the α track of 60 nm radius. The intensity of the delayed component of the scintillation has a stronger dependence on the electric field strength and on temperature. The implications of these data on the mechanisms affecting scintillation in liquid helium are discussed.

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Section: Temperature and Electric Field Dependence Of Afterpulse Smentioning

confidence: 99%

Effect of an electric field on superfluid helium scintillation produced byα-particle sources

et al. 2012

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“…The long lifetimes of 2 1 S and 2 3 S (20 ms [13] and 7900 s [14]) allow the 2S atoms to travel the 3.5-m distance to the end of the apparatus. Excited states that decay to 1 1 S produce 20-to-25-eV UV photons, and the purpose of the Ar-filled detector in Fig.…”

Section: Metastable Helium Sourcementioning

confidence: 99%

Selective detection of metastable helium atoms by elastic scattering collisions

et al. 2012

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A method for efficient and selective detection of 2 1 S and 2 3 S metastable He atoms is presented. Elastic collisions with Ar atoms in a diffuse gas spatially separate these 2S atoms from the copropagating UV photons that are inherently present in metastable beams. The deflected 2S atoms are detected on a large-solid-angle Faraday cup. A He discharge lamp can selectively quench 2 1 S atoms, and optical pumping together with a Stern-Gerlach magnet can selectively remove 2 3 S atoms. As a result, we are able to efficiently detect either 2 1 S or 2 3 S atoms (or both) without a UV background.

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“…Because single-photon decays are strictly forbidden for such a J = 0-0 transition, the decay proceeds by the emission of two photons [23][24][25]. Two measurements of the decay rate have been done on neutral He atoms [26,27], the latter (on a thermal atomic beam) reaching a precision of about 5%. The first measurement of this lifetime in any He-like ion, by Prior and Shugart [28], yielded a lifetime of (503 ± 26) µs.…”

Section: Introductionmentioning

confidence: 99%

Heavy-ion storage-ring quest for atomic lifetimes in Li⁺ and Be²⁺

Gwinner¹,

Knystautas²,

Wolf³

2003

Can. J. Phys.

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Decays of metastable levels in the He-like ions Li + and Be 2+ were studied at a heavy-ion storage ring. The lifetimes involved span five orders of magnitude (from 0.5 ms to 50 s) and thus test the performance envelope of the experimental technique. For the 1s2s 3 S 1 level in Be 2+ ions, our lifetime result of (1.80 ± 0.05) s agrees with accurate nonrelativistic and relativistic calculations. While theory in these cases is expected to be well developed, experience reflects on the capabilities of the experimental arrangement. The time-resolved observations reveal information on cross sections for collisional 39.90.+d, 31.50.+w Résumé : La désexcitation des niveaux métastables dans les ions héliumoïdes Li + et Be 2+ a été étudiée dans un anneau de stockage d'ions lourds. Les durées de vie correspondantes couvrent une étendue de cinq ordres de grandeur (de 0,5 ms à 50 s) repoussant ainsi les limites de cette technique expérimentale. Pour le niveau 1s2s 3 S 1 de l'ion Be 2+ , notre durée de vie mesurée de (1,80 ± 0,05) s est en accord avec des calculs précis relativistes ainsi que non-relativistes. La théorie reposant sur des bases solides dans de tels cas, l'étude néanmoins démontre le bien-fondé de cette approche expérimentale. Les mesures avec résolution temporelle ont permis l'obtention des résultats sur les sections efficaces de désexcitation par collisions.

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Radiative Lifetime of the2 S01Metastable State of Helium

Cited by 97 publications

References 19 publications

Effect of an electric field on superfluid helium scintillation produced byα-particle sources

Effect of an electric field on superfluid helium scintillation produced byα-particle sources

Selective detection of metastable helium atoms by elastic scattering collisions

Heavy-ion storage-ring quest for atomic lifetimes in Li⁺ and Be²⁺

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Radiative Lifetime of the2 S01Metastable State of Helium

Cited by 97 publications

References 19 publications

Effect of an electric field on superfluid helium scintillation produced byα-particle sources

Effect of an electric field on superfluid helium scintillation produced byα-particle sources

Selective detection of metastable helium atoms by elastic scattering collisions

Heavy-ion storage-ring quest for atomic lifetimes in Li+ and Be2+

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Product

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Heavy-ion storage-ring quest for atomic lifetimes in Li⁺ and Be²⁺