The angular distributions of the gamma radiation from the Li7(p,γ)Be8 reaction from Ep = 200 keV

Mainsbridge, B.

doi:10.1016/0029-5582(60)90023-7

Cited by 40 publications

(14 citation statements)

References 12 publications

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“…5a together with previous results of Mainsbridge [16] (dotted curve) sphere phase differences between s-and p-waves, and ~ is an energy-independent background phase used as a free parameter; this background phase could arise from distant resonances, such as the giant dipole resonance [-4] at E e -~ 5 MeV (F ~-4 MeV) leading to ~ -30 ~ The parameters for the resonant and DC terms were obtained from Table 2. The results are shown by the solid curve in Figure 5a, for ~ = 25 ~ and verify the recent explanation [3] of the observed forward-backward anisotropy at Ep = 80 keV [1] as caused by the interference between the E1 amplitude due to the DC process and the M1 amplitude due to the low-energy tail of the ER = 441 keV resonance.…”

Section: Forward-backward Anisotropiessupporting

confidence: 76%

The S(E) factor of7Li(p, ?)8Be and consequences for S(E) extrapolation in7Be(p, ?0)8B

Zahnow

Angulo²,

Rolfs

et al. 1995

Z. Physik A - Hadrons and Nuclei

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Abstract. Excitation functions and forward-backward an-isotropies have been measured for the 7Li(p, ~)SBe capture reaction over the proton energy range Ep = 100 to 1500 keV, using a 4~z summing crystal and Ge(Li) detectors, respectively. The data show at all energies the presence of E1 and M1 capture amplitudes arising from the direct capture (DC) process and the ER----441 and 1030 keV resonances, respectively. Due to the observed DC process, the present data increase significantly the reaction rates (up to a factor of 110) compared to values given in the compilation. The data and their analyses remove the recent criticism on DC model calculations, which had implied a significant reduction in the extrapolated S(E) factor for 7Be(p, y)SB and thus in the predicted flux of high-energy solar neutrinos; thus, the solar neutrino problem is still with us. 25.40 vanishing M1 (p+p) amplitude at thermal energies, caused by the p-wave centrifugal barrier in the entrance channel. Consequently, a similar significant reduction was also suggested [1] in the predicted flux of high-energy solar neutrinos. PACS:In view of these important consequences, a recent note discussed [31 another possible source of the observed M1 capture amplitude in VLi(p, 7o)SBe at Ep = 80 keV; evidence was given that the amplitude arises predominantly from the low-energy tail of the known J~ = 1 + ER = 441 keV resonance [4] and that therefore the above criticism on DC model calculations, used also in the extrapolation of S(E) data in 7Be(p, 7)SB, is not valid. To clarify definitely this situation, improved 7Li(p, 70)SBe data were desirable, i.e., forward-backward anisotropies and excitation functions, over a wide range of proton energies including (or approaching) Ep = 80 keV. The present paper reports on such data.

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Section: Forward-backward Anisotropiessupporting

confidence: 76%

The S(E) factor of7Li(p, ?)8Be and consequences for S(E) extrapolation in7Be(p, ?0)8B

Zahnow

Angulo²,

Rolfs

et al. 1995

Z. Physik A - Hadrons and Nuclei

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“…The 6.05 MeV E0 transition from 16 O is present due to the 19 F(p, α) 16 O reaction on the fluorine content of the target. The 11 MeV peak contains M1 and E1 transitions in 28 Si.…”

Section: Resultsmentioning

confidence: 98%

“…It is known that the 18.15 MeV transition has a very large (8:1) forward-backward anisotropy [16,17], which is caused by the interference of the E1 amplitude due to the direct capture process and the M1 amplitude of the 441 keV and 1030 keV resonances. We investigated their possible effects on the angular correlation of the e + -e − pairs as well.…”

Section: Resultsmentioning

confidence: 99%

Observation of Anomalous Internal Pair Creation in $^8$Be

Gácsi

Csatlós

Ketel³

et al. 2015

Acta Phys. Pol. B Proc. Suppl.

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The electron-positron angular correlation was measured for the isoscalar magnetic dipole 18.15 MeV transition in 8 Be. Significant, peak-like deviation was observed from the internal pair creation at Θ ≈ 140• in the angular correlation. This observation might indicate that in an intermediate step a neutral isoscalar particle with a mass of 16.70±0.35 (stat.)±0.5(sys.) MeV/c 2 and J π = 1 + was created.

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“…Transformations of these results into a channel spin (L S) co-upling scheme (rather than j-j coupling used so far), where the notation '+'lJ denotes the scattering state quantum numbers (where j = I + s), via the prescription in Seyler and Weller [14], are also presented in Table I. In the channel spin coupling notation, the p-wave Ml strengths are in a ratio of 1/5, for spins 1 and 2, respectively, within their statistical errors, as was seen by Mainsbridge [4] The results of fitting the data using only s-wave E1 and p-wave E2 radiations are summarized in Table II. All fits presented so far, except the slg El and pily M1 only fits, produced the same Legendre coefficients which resulted in identical cr(8)/Ao and As(8) curves. These curves are all plotted in Fig.…”

mentioning

confidence: 85%

“…Indeed, previous work has been analyzed based on this assumption [3]. Prior to this, the strong 17.640 MeV [E~(lab) = 441 keV] resonance of sBe was shown to be a 1+ (T = 1) state formed via p-wave capture with subsequent M1 decay to the ground state of sBe [4]. Angular distribution data indicated that the two p-wave amplitudes, with channel spins 1 and 2, occurred in the ratio of 1 to 5 (which was not explained).…”

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confidence: 99%

Observation of Substantialp-Wave Capture Strength in theLi7(

1994

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The 7Li(p, y)SBe reaction has been studied using polarized protons having an incident energy in the range E~(lab) = 80 -0 keV. The measured angular distributions of the cross section cr(8)/Ao and analyzing power AY(8) were interpreted using a model independent transition-matrix element analysis.The large (-40%) analyzing power at 90' indicates the presence of an appreciable p-wave capture strength at these energies. The direct-capture model is used to show that this could reduce the astrophysical S factor by as much as 40%. PACS numbers: 25.40.Lw, 24.70.+s, 95.30.CqThe radiative capture of low energy protons on Li to excited states of Be is of interest for several reasons. Understanding the dynamics of the capture process is in itself worthwhile. And this understanding should lead to a more accurate and reliable extraction of the astrophysical S factor and the thermonuclear reactivity for the 7Li(p, y)sBe reaction. In addition, isospin symmetries can be used to relate the 7Li(p, y)sBe reaction to the 7Be(p, y) B reac-

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The angular distributions of the gamma radiation from the Li7(p,γ)Be8 reaction from Ep = 200 keV

Cited by 40 publications

References 12 publications

The S(E) factor of7Li(p, ?)8Be and consequences for S(E) extrapolation in7Be(p, ?0)8B

The S(E) factor of7Li(p, ?)8Be and consequences for S(E) extrapolation in7Be(p, ?0)8B

Observation of Anomalous Internal Pair Creation in $^8$Be

Observation of Substantialp-Wave Capture Strength in theLi7(

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