Measurement of 23Mg+p resonance energies

Dale Visser, ORNL Physics Division
Chris Wrede, Yale University
Jac Caggiano, Yale University
Jason Clark, Yale University
Catherine Deibel, Yale University
Rachel Lewis, Yale University
Anuj Parikh, Yale University
Peter Parker, Yale University


Two inconsistent sets of 24Al excitation-energy measurements have been used to determine resonance energies for the 23Mg(p, γ)24Al reaction. This discrepancy results in a factor of five variation in the calculated thermonuclear 23Mg(p, γ) 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 have measured 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 Ecm. = 474(6) keV for what is thought to be the most important 23Mg(p, γ)24Al resonance astrophysically [the previous measurements yielded values of E c.m. = 499(5) and 458(10) keV]. A more precise thermonuclear 23Mg(p, γ)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. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlikeLicence.