Spectroscopy ofAl24and extraction of Gamow-Teller strengths with theMg24

Abstract

The 24 Mg( 3 He,t) 24 Al reaction has been studied at E( 3 He) = 420 MeV. An energy resolution of 35 keV was achieved. Gamow-Teller strengths to discrete levels in 24 Al are extracted by using a recently developed empirical relationship for the proportionality between Gamow-Teller strengths and differential cross sections at zero momentum transfer. Except for small discrepancies for a few weak excitations, good agreement with previous 24 Mg(p, n) data and nuclear-structure calculations using the USDA/B interactions in the sd shell-model space is found. The excitation energy of several levels in 24 Al of significance for determination of the 23 Mg(p, γ) 24 Al thermonuclear reaction rate were measured. Results are consistent with two of the three previous ( 3 He,t) measurements, performed at much lower beam energies. However, a new state at Ex( 24 Al)=2.605(10) MeV was found and is the third state above the proton separation energy.

Ab initio calculations of Gamow-Teller strengths in the sd shell

“…This reaction gives the strongest peak at the excitation energy 1. 35 MeV with nearly the same B(GT ) value as obtained from the 24 Mg(t, 3 He) 24 Na reaction. Some other peaks are also observed with less strength.…”

“…The experimental information on the B(GT ) strength distribution for the transition 24 Mg → 24 Al is available from the 24 Mg( 3 He,t) 24 Al reaction observed at 420 MeV [35], and the 24 Mg(p,n) 24 Al reaction observed at 136 MeV [34]. The results of the shell model calculation for the B(GT ) strength have been previously reported in Ref.…”

“…The results of the shell model calculation for the B(GT ) strength have been previously reported in Ref. [35], where the phenomenological interactions USDA and USDB were employed. Fig.…”

Nuclear astrophysics with radioactive beams

“…Charge-exchange reactions, however, can map the GT strength distributions over a wider range of excitation energies. A variety of charge-changing reactions can be employed, for example, A Z(p, n) A (Z+1) [423,171], A Z(n, p) A (Z − 1) [424], A Z(d, 2 He) A (Z − 1) [425], A Z( 3 He, t) A (Z + 1) [426][427][428][429], and A Z(t, 3 He) A (Z − 1) [430][431][432][433]. In chargeexchange reactions at beam energies exceeding 100 MeV/nucleon, the cross-section at low momentum transfer (small angles) is proportional to the B(GT ) transition strength [434][435][436]171,173].…”

Gamow-Teller strengths of some sd-shell nuclei in the shell model framework

“…They also compared their theoretical results from the two mentioned approaches with the shell model calculations using the phenomenological USDB effective interaction [11]. Zegers et al, studied [12] the 24 Mg( 3 He,t) 24 Al reaction at E( 3 He)=420 MeV. An energy resolution of 35 keV was achieved.…”