Structure of resonances in the Gamow burning window for theAl25(p,γ)Si26reaction in nov

Abstract

A γ-ray spectroscopy study of excited states in 26 Si has been performed using the 24 Mg( 3 He,n) reaction at a beam energy of 10 MeV. In particular, states have been studied above the proton threshold relevant for burning in the 25 Al(p,γ) 26 Si reaction in novae. This reaction influences the amount of 26 Al injected into the interstellar medium by novae, which contributes to the overall flux of cosmic gamma-ray emission from 26 Al observed in satellite missions. The present results point strongly to the existence of a 0 + state at an excitation energy of 5890 keV lying within the Gamow burning window, which raises questions about the existence and properties of another, higher-lying state/resonance reported in previous experimental work. The existence of two such states within this excitation energy region cannot be understood in the framework of sd shell-model calculations.

β-delayedγdecay ofP26: Possible evidence of a proton halo

“…However, it is worth mentioning a significant discrepancy (up to 6 keV) with energies obtained in Refs. [51,53] for the two γ rays emitted from the 4 agreement with our results. However, it should be noted that the γ-ray branching ratios are inconsistent for the 1759.7-keV transition.…”

“…We compare in Table IV the energies and the spins and parities deduced in this work with previous values available in the literature [8,[51][52][53]. The results of Ref.…”

Study of the $${{^{25}}}$$Mg(d,p)$${{^{26}}}$$Mg reaction to constrain the $${{^{25}}}$$Al(p,$${\gamma }$$)$${{^{26}}}$$Si resonant reaction rates in nova burning conditions

“…[16,43], were based on shell-model calculations [45]). For the excitation energy of the 0 + state, we have used the value of 5.890 MeV adopted in the most recent data compilation [23], based on several recent γ-decay measurements [40][41][42], to derive the resonance energy and estimate the proton partial width (an earlier ( 3 He, n) neutron time-of-flight measurement had assigned the 0 + state an excitation energy of 5.946 MeV [43]).…”

New constraints on the Al25(p,γ) reaction and its influence on the flux of cosmic γ rays from classical nova explosions

“…For an evaluation of the 25 Al(p, γ ) stellar reaction rate, we consider the contribution of resonant states in 26 Si at 5675, 5890, 5928, and 5950 keV [23], respectively, (direct capture is expected to be negligible for temperature 0.1 GK). The recently reported isotropic angular distributions of γ decays from the 5890-keV level in 26 Si [28] indicate a good isobaric pairing with the 0 + 4 6256-keV excited state in 26 Mg, whereas the 1 + 1 5675-and 3 + 3 5928-keV states have already been previously well matched to analog states in 26 Mg at 5691 and 6125 keV [29], respectively. In contrast, the spin-parity assignment of the 5950-keV level in 26 Si remains somewhat controversial.…”

“…Previous studies of the 25 Al(p, γ ) 26 Si reaction [5,[22][23][24][25][26][27][28][29][30][31][32][33] indicate that the rate is dominated by resonant capture to excited states in 26 Si above the proton-emission threshold energy of 5513.99 (13) keV [34]. Specifically, a 3 + 5927.6(10)-keV level in 26 Si, corresponding to a = 0 capture resonance on the 5/2 + ground state of 25 Al, is expected to make the most significant contribution.…”