Multielectron effects in capture of antiprotons and muons by helium and neon

Cohen, James S.

doi:10.1103/physreva.62.022512

Cited by 53 publications

(86 citation statements)

References 49 publications

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“…7). Relatively little metastable populations were detected in states with n ജ 41, whereas theoretical calculations [21][22][23][24][25][26][27][28] predict significant populations in states up to n ജ 50. As these theoretical populations do not take the effect of collisions between pHe + and helium atoms into account, however, they may not be directly comparable with the experimental results presented here which refer to atoms thermalized by many collisions.…”

Section: A Primary Populationsmentioning

confidence: 99%

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Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯
Hori
¹
,
Eades
²
,
Widmann
³

et al. 2004
Phys. Rev. A
35
2
23
0
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The time evolution of the state populations in the v ϵ n − ᐉ −1=2 and 3 metastable cascades of antiprotonic helium (p 4 He + ) atoms were studied using laser spectroscopy. The antiprotonic states ͑n , ᐉ͒ = ͑39, 35͒, (40,36), and (41,37) in the v = 3 cascade were estimated to initially contain, respectively, ͑0.28± 0.04͒%, ͑0.06± 0.02͒%, and ͑0.02± 0.01͒% of the antiprotons stopped in the helium target, while the corresponding values for states ͑37, 34͒, ͑38, 35͒, and ͑39, 36͒ in the v = 2 cascade were ͑0.21± 0.04͒%, ͑0.49± 0.07͒%, and ͑0.19± 0.07͒%. The shortening of the state lifetimes due to collisions between pHe + and helium atoms was studied. As the atomic density of the target was increased from =2ϫ 10 20 to 2 ϫ 10 21 cm −3 , the lifetime of state ͑37, 34͒ decreased by an order of magnitude, whereas the higher states ͑38, 35͒ and ͑39, 35͒ were relatively unaffected. Between densities =6ϫ 10 20 and 2 ϫ 10 22 cm −3 , a short-lived component with a time constant ϳ 0.2 s appeared at early times in the delayed annihilation time spectrum of pHe + , while the total fraction of long-lived antiprotons decreased from 3.0 to 2.5%. These effects were caused by the lifetime-shortening of specific pHe + states such as ͑37, 34͒.

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Section: A Primary Populationsmentioning

confidence: 99%

“…(i) Capture: when an antiproton collides with a helium atom at electron-volt energies, it may replace one of the electrons orbiting the helium nucleus, and become captured into a pHe + state. This occurs [12,[20][21][22][23][24][25][26][27][28] with the highest probability into states with n-values of about n ϳ n 0 ϵ ͱ M * /m e = 38.3…”

Section: Introductionmentioning

confidence: 99%

Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯
Hori
¹
,
Eades
²
,
Widmann
³

et al. 2004
Phys. Rev. A
35
2
23
0
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“…The cascade process has been studied by measuring time evolutions of the populations in many states with n ≤ 40 [6,7]. Here we similarly study the population in the state (40,36) scopy of antiprotonic helium is the main subject of this review, and we tline of the method involved and the results obtained.…”

mentioning

confidence: 99%

Observation of the 1154.9 nm transition of antiprotonic helium

Kobayashi

Barna

Hayano

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. The resonance transition (n, l) = (40, 36) → (41, 35) of the antiprotonic helium (p 4 He + ) isotope at a wavelength of 1154.9 nm was detected by laser spectroscopy. The population of p 4 He + occupying the resonance parent state (40, 36) was found to decay at a rate of 0.45 ± 0.04 µs −1 , which agreed with the theoretical radiative rate of this state. This implied that very few long-lived p 4 He + are formed in the higher-lying states with principal quantum number n ≥ 41, in agreement with the results of previous experiments.

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“…Several theoretical calculations [20][21][22][23][24][25] (two such results are shown in Fig. 5) predict that T e is small with respect to I 0 .…”

mentioning

confidence: 99%

Primary Populations of Metastable AntiprotonicH4eandH
Hori
¹
,
Eades
²
,
Hayano
³

et al. 2002
Phys. Rev. Lett.

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Initial distributions of metastable antiprotonic 4 He and 3 He atoms over principal (n) and angular momentum (') quantum numbers have been deduced using laser spectroscopy experiments. The regions n 37-40 and n 35-38 in the two atoms account for almost all of the observed fractions [ 3:0 0:1 % and 2:4 0:1 %] of antiprotons captured into metastable states. DOI: 10.1103/PhysRevLett.89.093401 PACS numbers: 36.10.-k, 25.43.+t, 34.90.+q A negatively charged particle X ÿ (such as ÿ , ÿ , or p) approaching an atom at electron-volt energies can displace one of its electrons, thereby forming an exotic atom [1]. Little is known about the principal (n) and angular momentum (') quantum numbers of the atom's primordial (i.e., initially occupied) states. It has been widely believed since the 1950s [2-4] that in exotic hydrogen and helium atoms, n will be distributed around the value(M being the reduced mass of the X ÿ -nucleus system, and m e the electron mass), which corresponds to the X ÿ orbital with the same radius and binding energy as that of the displaced 1s electron. In this paper, we describe measurements of the n; ' distributions of antiprotons captured into atomic states in metastable antiprotonic helium [5][6][7][8], including the isotopes p 4 He for which n 0 38:3 and p 3 He for which n 0 37:1. These pHe states (see Fig. 1) have microsecond-scale lifetimes against annihilation, because their large ' values (' n ÿ 1) do not permit them to deexcite by Auger emission of the electron. Instead, the atoms slowly undergo a series of constant v n ÿ ' ÿ 1 radiative transitions (i.e., n ' ÿ1). They finally reach states which proceed rapidly to pHe 2 ions, which are immediately destroyed by collisional Stark effects. So far, the numbers of antiprotons populating two metastable states in p 4 He [namely, n; ' 39; 35 and 37; 34 ] have been measured [9,10] using laser spectroscopic methods [11] at the former LEAR facility at CERN. The two states represent only a small fraction of the totality of metastable states shown in Fig. 1; moreover, since for technical reasons [9] the populations could be measured only after a minimum delay of t 1:8 s following atomic formation, the primary populations (those at t 0) could not be reliably estimated. We study here a total of 20 transitions in p 4 He and p 3 He atoms starting at t 300 ns, and estimate the primary populations in nearly all the metastable states.These experiments were made at the Antiproton Decelerator at CERN, the setup [12] being an extension of our former one. Metastable pHe atoms were produced

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Multielectron effects in capture of antiprotons and muons by helium and neon

Cited by 53 publications

References 49 publications

Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯
Hori
¹
,
Eades
²
,
Widmann
³

et al. 2004
Phys. Rev. A
35
2
23
0
View full text Add to dashboard Cite

Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯
Hori
¹
,
Eades
²
,
Widmann
³

et al. 2004
Phys. Rev. A
35
2
23
0
View full text Add to dashboard Cite

Observation of the 1154.9 nm transition of antiprotonic helium

Primary Populations of Metastable AntiprotonicH4eandH
Hori
¹
,
Eades
²
,
Hayano
³

et al. 2002
Phys. Rev. Lett.

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Multielectron effects in capture of antiprotons and muons by helium and neon

Cited by 53 publications

References 49 publications

Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯Hori1, Eades2, Widmann3 et al. 2004Phys. Rev. A352230View full textAdd to dashboardCite

Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯Hori1, Eades2, Widmann3 et al. 2004Phys. Rev. A352230View full textAdd to dashboardCite

Observation of the 1154.9 nm transition of antiprotonic helium

Primary Populations of Metastable AntiprotonicH4eandHHori1, Eades2, Hayano3 et al. 2002Phys. Rev. Lett.

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Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯
Hori
¹
,
Eades
²
,
Widmann
³

et al. 2004
Phys. Rev. A
35
2
23
0
View full text Add to dashboard Cite

Populations and lifetimes in thev=n−ℓ−1=2and 3 metastable cascades ofp¯
Hori
¹
,
Eades
²
,
Widmann
³

et al. 2004
Phys. Rev. A
35
2
23
0
View full text Add to dashboard Cite

Primary Populations of Metastable AntiprotonicH4eandH
Hori
¹
,
Eades
²
,
Hayano
³

et al. 2002
Phys. Rev. Lett.