出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Two inconsistent sets of 24Al excitation-energy measurements have been used to determine resonance
energies for the 23Mg(p,g )24Al reaction. This discrepancy results in a factor of five variation
in the calculated thermonuclear 23Mg(p,g )24Al reaction rate at T = 0.25 GK, and presents
a challenge to an imminent radioactive ion-beam measurement of this reaction that will rely on
precisely known resonance energies. We havemeasured the 24Mg(3He,t)24Al reaction using a 30-
MeV 3He beam from the tandem Van de Graaff accelerator at Yale University’s Wright Nuclear
Structure Laboratory. The Yale Enge magnetic spectrograph was used to momentum-analyze
reaction products; a position-sensitive ionization drift chamber backed by a scintillator at the
focal plane was used to identify tritons and measure the excitation energies of corresponding
states in 24Al. We find good general agreement with one of the two previous sets of measurements
and determine an energy of Ec.m. = 474(6) keV for what is thought to be the most important
23Mg(p,g )24Al resonance astrophysically [the previous measurements yielded values of
Ec.m. = 499(5) and 458(10) keV]. A more precise thermonuclear 23Mg(p,g )24Al rate will help
to constrain the determination of nuclear flow out of the NeNa cycle, and production of A ≥ 20
nuclides, in explosive hydrogen burning over a temperature range 0.2 < T < 1.0 GK.
