Abstract
The rate of the ^{25}Al(p, gamma )^{26}Si reaction is one of the few key remaining nuclear uncertainties required for predicting the production of the cosmic gamma -ray emitter ^{26}Al in explosive burning in novae. This reaction rate is dominated by three key resonances (J^{pi }=0^{+}, 1^{+} and 3^{+}) in ^{26}Si. Only the 3^{+} resonance strength has been directly constrained by experiment. A high resolution measurement of the ^{25}Mg(d, p) reaction was used to determine spectroscopic factors for analog states in the mirror nucleus, ^{26}Mg. A first spectroscopic factor value is reported for the 0^{+} state at 6.256 MeV, and a strict upper limit is set on the value for the 1^{+} state at 5.691 MeV, that is incompatible with an earlier (^{4}He, ^{3}He) study. These results are used to estimate proton partial widths, and resonance strengths of analog states in ^{26}Si contributing to the ^{25}Al(p, gamma )^{26}Si reaction rate in nova burning conditions.
Highlights
Classical novae involve a thermonuclear runaway and the ejection of material whenever a white dwarf in a binary stellar system has accreted sufficient material from its companion star [12] and have been predicted to occur at a galactic rate of 50−+2331 per year [13]. 26Al is produced by a series of proton capture reactions and β-decays during explosions that reach temperatures in the range of 0.1–0.4 GK [14]
In this paper we have presented the results of a 25Mg(d, p)26Mg experimental reaction study performed at Triangle Universities Nuclear Laboratory (TUNL) using the Enge split-pole spectrometer
From our study we have been able to measure a first value of the spectroscopic factor for the (d, p) reaction to the 0+ state in 26Mg
Summary
Classical novae involve a thermonuclear runaway and the ejection of material whenever a white dwarf in a binary stellar system has accreted sufficient material from its companion star [12] and have been predicted to occur at a galactic rate of 50−+2331 per year [13]. 26Al is produced by a series of proton capture reactions and β-decays during explosions that reach temperatures in the range of 0.1–0.4 GK [14]. The 25Al( p, γ )26Si reaction rate can become faster than 25Al β-decay. In this scenario 26Si subsequently β-decays to the short lived 0+ isomeric state of 26Al, leading to the bypassing of the production of the ground state. The 25Al( p, γ )26Si reaction rate at nova burning temperatures is expected to be dominated by three resonances in 26Si corresponding to excitation energies of 5.676 (spin/parity J π = 1+), 5.890 (0+) and 5.929 (3+) MeV. Direct measurements of the individual resonance strength contributions to the 25Al( p, γ )26Si reaction rate are not feasible with presently available 25Al radioactive beam intensities.
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