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The two charge exchange reactions 14N(d, 2He)14C and 14N(3He, t)14O were studied with high resolution in order to identify the Gamow–Teller (GT) strength distribution starting from the ground state (g.s.) of 14N in the β− and β+ directions. The isospin symmetry in the A = 14 mass system is investigated. An overview of the main features of the experimental investigation is summarized here.

In order to study the Gamow–Teller (GT) transitions in the fp-shell nucleus 64Cu, the 64Ni(3He, t)64Cu charge-exchange reaction was investigated at MeV/nucleon [1]. The outgoing tritons were momentum analysed by the Grand Raiden spectrometer at 0. The very high energy resolution of 35 keV (FWHM) allowed the separation of individual levels in the excitation energy region from 0 to 3.5 MeV. An angular distribution analysis was performed for the observed transitions to these states. In addition to the ground state (g.s.), known to be a Jπ = 1+ GT state, several excited states showed L = 0 nature, making them candidates of GT states. At higher excitation energies, the level density becomes very high and a bump-like structure, the so-called GT Giant Resonance, dominates the spectrum.

Abstract:: Under the assumption that isospin is a good quantum number, symmetry is expected for the transitions from the ground states of T = 1, T z = ±1 nuclei to the common excited states of the T z = 0 nucleus situated between the two nuclei. The symmetry can be studied by comparing the strengths of Gamow-Teller (GT) transitions obtained from a (p, n)-type charge-exchange reaction on a target nucleus with T z = 1 with those from the β-decay of the T z = - 1 nucleus. The A = 58 system is the heaviest for which such a comparison is possible. As a part of the symmetry study, we measured the GT transitions from 58Ni (T z = 1) to 58Cu (T z = 0) by using the zero-degree (3 He, t) reaction at 150 MeV/nucleon. With the achieved resolution of 50 keV, many hitherto unresolved GT states have been identified. The GT transition strengths were obtained for states up to 8 MeV excitation, i.e., near to the Q window limitation ( Q EC = 9.37 MeV) of the β-decay from 58Zn (T z = - 1) to 58Cu. The strength distribution is compared with that from shell-model calculations.

Assuming isospin T is a good quantum number, the analog states of the low-lying states in Tz = ±(T0+1) nuclei can be found as excited T0+1 states in Tz= ±T0 nuclei. Therefore, if T0+1 states are identified in the excited region of Tz= ±T0 nuclei, the structure of unstable nuclei with Tz = ±(T0+1) can be deduced. We measured and compared the transition strengths to pairs of excited analog states in inelastic and charge-exchange reactions on the same target nucleus. The T values of these analog states were identified by using the fact that the transition strengths to them are different depending on T. The identification of T = 1/2 and 3/2 nature of analog M1 and GT states in the mirror nuclei pair 27Al and 27Si is reported by comparing the transition strengths in high-resolution 27Al(p,p′) and 27Al(3He,t)27Si reactions at 0°. The identified T = 3/2 states are analogous to the low-lying states of 27Mg, which plays an important role in rp-process of nucleosynthesis.