The 25Mg(p, γ)26Al and 25Mg(p, p′) resonances for Ep = 0.31–1.84 MeV

doi:10.1016/0375-9474(86)90056-4

Nuclear Physics A

Volume 459, Issue 1, 27 October 1986, Pages 61-76

https://doi.org/10.1016/0375-9474(86)90056-4 Get rights and content

Abstract

Thin target yield curves with good statistics have been measured for the ²⁵Mg(p, γ)²⁶Al and ²⁵Mg(p, p′)²⁵Mg reactions in the E_p = 310–1845 keV region. Altogether 76 resonances have been observed, of which 45 only in (p, γ), 30 in both (p, γ) and (p, p′), and one only in (p, p′). Several of these resonances had not been observed previously in either of the two reactions, and several of the previously observed resonances turned out to be doublets. All 39 ²⁵Mg(p, p₀)²⁵Mg resonances found previously in the E_p = 700–1845 keV region resonate in (p, γ) and many also in (p, p′). Resonance strengths have been derived relative to that of the E_p = 593 keV resonance.

The analysis of weak (p, p₁) and (p, p₂) resonance yields has been supported by a calculation of the yields in the continuum (in between resonances) due to the Breit-Wigner tails of strong and broad resonances in the neighbourhood (with interference between resonances with the same J^π; T taken into account), and to Coulomb excitation.

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Cited by (68)

First result from the Jinping Underground Nuclear Astrophysics experiment JUNA: precise measurement of the 92 keV 25Mg(p, γ)26Al resonance
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The ²⁵Mg(p, $γ$ )²⁶Al reaction plays an important role in the study of cosmic 1.809 MeV $γ$ -ray as a signature of ongoing nucleosynthesis in the Galaxy. At astrophysical temperature around 0.1 GK, the ²⁵Mg(p, $γ$ )²⁶Al reaction rates are dominated by the 92 keV resonance capture process. We report a precise measurement of the 92 keV ²⁵Mg(p, $γ$ )²⁶Al resonance in the day-one experiment at Jinping Underground Nuclear Astrophysics experiment (JUNA) facility in the China Jinping Underground Laboratory (CJPL). The resonance strength and ground state feeding factor are determined to be $3.8 \pm 0.3$ ×10⁻¹⁰ eV and $0.66 \pm 0.04$ , respectively. The results are in agreement with those reported in the previous direct underground measurement within uncertainty, but with significantly reduced uncertainties. Consequently, we recommend new ²⁵Mg(p, $γ$ )²⁶Al reaction rates which are by a factor of 2.4 larger than those adopted in REACLIB database at the temperature around 0.1 GK. The new results indicate higher production rates of ^26gAl and the cosmic 1.809 MeV $γ$ -ray. The implication of the new rates for the understanding of other astrophysical situations is also discussed.
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The measurement of a reaction cross section from a pulse height spectrum is a ubiquitous problem in experimental nuclear physics. In γ-ray spectroscopy, this is accomplished frequently by measuring the intensity of full-energy primary transition peaks and correcting the intensities for experimental artifacts, such as detection efficiencies and angular correlations. Implicit in this procedure is the assumption that full-energy peaks do not overlap with any secondary peaks, escape peaks, or environmental backgrounds. However, for complex γ-ray cascades, this is often not the case. Furthermore, this technique is difficult to adapt for coincidence spectroscopy, where intensities depend not only on the detection efficiency, but also the detailed decay scheme. We present a method that incorporates the intensities of the entire spectrum (e.g., primary and secondary transition peaks, escape peaks, Compton continua, etc.) into a statistical model, where the transition intensities and branching ratios can be determined using Bayesian statistical inference. This new method provides an elegant solution to the difficulties associated with analyzing coincidence spectra. We describe it in detail and examine its efficacy in the analysis of ¹⁸O(p,γ)¹⁹F and ²⁵Mg(p,γ)²⁶Al resonance data. For the ¹⁸O(p,γ)¹⁹F reaction, the measured branching ratios improve upon the literature values, with a factor of 3 reduction in the uncertainties.
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Citation Excerpt :
To the best of our knowledge there is only one set of data published by Boni et al. [20] available in the literature for Mg that can be compared with the present measurements. Four other data sets are available but as thick target yields for several selected energies [23–25] or as continuum cross section presented only in the graphical form in the original publication [26] but anyway limited to 1.85 MeV proton energy. Comparison of our results with the results from Ref. [20] is shown at Figs. 4 and 5.
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The 25Mg(p, γ) 26Al reaction at low astrophysical energies
2012, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
In the present work we report on a new measurement of resonance strengths ωγ in the reaction ²⁵Mg(p, γ)²⁶Al at $E_{cm} = 92$ and 189 keV. This study was performed at the LUNA facility in the Gran Sasso underground laboratory using a 4π BGO summing crystal. For the first time the 92 keV resonance was directly observed and a resonance strength $ω γ = (2.9 \pm 0.6) \times 10^{- 10} eV$ was determined. Additionally, the γ-ray branchings and strength of the 189 keV resonance were studied with a high resolution HPGe detector yielding an ωγ value in agreement with the BGO measurement, but 20% larger compared to previous works.
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A recent Penning-trap measurement of the masses of ${}^{46}V$ and ${}^{46}{Ti}$ leads to a $Q_{EC}$ value that disagrees significantly with the previously accepted value, and destroys overall consistency among the nine most precisely characterized $T = 1$ superallowed $β$ emitters. This raises the possibility of a systematic discrepancy between Penning-trap measurements and the reaction-based measurements upon which the $Q_{EC}$ values depended in the past. We carefully re-analyze ( $n, γ$ ) and ( $p, γ$ ) reaction measurements in the $24 \leq A \leq 28$ mass region, and compare the results to very precise Penning-trap measurements of the stable nuclei ${}^{24}{Mg}$ , ${}^{26}{Mg}$ and ${}^{28}{Si}$ . We thus determine upper limits to possible systematic effects in the reaction results, and go on to establish limits for the mass of radioactive ${}^{26}{Al}$ , to which future on-line Penning-trap measurements can be compared. We stress the urgency of identifying or ruling out possible systematic effects.

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Nuclear Physics A

Abstract

References (14)

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Nucl. Phys.

Nucl. Phys.

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Cited by (68)

First result from the Jinping Underground Nuclear Astrophysics experiment JUNA: precise measurement of the 92 keV <sup>25</sup>Mg(p, γ)<sup>26</sup>Al resonance

γ-Ray spectroscopy using a binned likelihood approach

Nuclear Data Sheets for A = 26

Measurements of proton induced γ-ray emission cross sections on MgF<inf>2</inf> target in the energy range 1.95-3.05 MeV

The <sup>25</sup>Mg(p, γ) <sup>26</sup>Al reaction at low astrophysical energies

Mass measurements and superallowed β decay