New experimental study of low-energy (p,γ) resonances in magnesium isotopes

Abstract

Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-shell burning. In particular, the strengths of low-energy resonances with E<200 keV in 25Mg(p,γ)26Al determine the production of 26Al and a precise knowledge of these nuclear data is highly desirable. Absolute measurements at such low energies are often very difficult and hampered by γ-ray background as well as changing target stoichiometry during the measurements. The latter problem can be partly avoided using higher-energy resonances of the same reaction as a normalization reference. Hence the parameters of suitable resonances have to be studied with adequate precision. In the present work we report on new measurements of the resonance strengths ωγ of the E=214, 304, and 326 keV resonances in the reactions 24Mg(p,γ)25Al, 25Mg(p,γ)26Al, and 26Mg(p,γ)27Al, respectively. These studies were performed at the LUNA facility in the Gran Sasso underground laboratory using multiple experimental techniques and provided results with a higher accuracy than previously achieved

TheN14(p,γ)Marta1, Formicola2, Bemmerer3 et al. 2011Phys. Rev. CSelf Cite

“…Also for E γ 3 MeV with proper shielding the γ -ray background has been found to be much lower than in comparable laboratories at the surface of the Earth [34]. The unique location of LUNA has enabled the study of several nuclear reactions of astrophysical importance [21,[35][36][37][38][39][40].…”

Longitudinal and transverse electron-nucleus scattering form factors ofMg25

“…Many papers have recorded the study of the slow-neutron-capture (s) process, an important source of neutrons within the reaction 22 Ne(α,n) 25 Mg. This reaction plays an important role during core helium burning, in carbon-shell burning [1][2][3], and is Mg-Al cycle active in stellar H -shell burning [4]. Recently, the nuclear structure of this isotope has been studied by a number of theoretical methods, all dealing with the hyperon in p orbit [5][6][7].…”

28Si(p,3He) reaction for spectroscopy ofChipps1, Bardayan2, Chae3 et al. 2012Phys. Rev. C15060View full textAdd to dashboardCite

“…The proton separation energy in 26 Al is 6306.45 ± 0.05 keV [33]. Several of the known lower-energy resonances in 25 Mg(p,γ) 26 Al were not populated in the 3 He spectrum: for instance, the 304-keV resonance at E x = 6598 keV [9], the 254-keV resonance at E x = 6551 keV, or the 198-keV resonance at E x = 6496 keV [4], and so branching ratios for comparison with such earlier measurements could not be obtained in this work. The levels for which proton branching ratios were measured, as well as the value of the branching ratio B p , are shown in Figure 6, and listed in Table II. The peaks observed in the proton-gated spectra were fit using the known peak-fit parameters from the singles data, unless statistics were such that a fit was unachievable.…”

“…The isotope 26 Al is important in many different fields of nuclear physics: in astrophysics for the study of 26 Al decay in the Galaxy [1][2][3][4][5][6][7][8][9][10], as an isotopic chronometer [11,12], and as a benchmark for superallowed Fermi β-decay studies of the weak interaction that probe the Standard Model [13,14], for example. In each case, the specific aspects of the structure of the 26 Al nucleus, including excitation energies, spin and parity assignments, branching ratios, spectroscopic factors, and lifetimes, are required for a full understanding of the mechanism being examined.…”