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The interaction cross-sections (σI) of neutron-rich Na isotopes, 23-35Na, on C target have been measured at 250A MeV using the RI beam factory (RIBF) at RIKEN. Mass dependence of σI for 27-35Na suggests monotonic growth of the skin thickness. The root-mean-square nuclear matter radii (r̃m) of 23-35Na were deduced from observed σI via a Glauber-type calculation. These r̃m are in a good agreement with the theoretical prediction by relativistic mean field model (RMF). r̃m of 33-35Na were determined for the first time. [ABSTRACT FROM AUTHOR]

Charge-exchange reactions at intermediate energies have been used extensively in nuclear structure studies as a sensitive probe of the spin-isospin response of nuclei. Experimental investigations have been mostly limited to stable targets. There are, however, compelling scientific arguments to extend these studies to unstable nuclei. The Low Energy Neutron Detection Array (LENDA) is designed to facilitate the study of (p, n) charge exchange reactions in inverse kinematics using unstable beams. The array, which is designed to measure neutron energies and angles with high detection efficiencies, is currently under development at the National Superconducting Cyclotron Laboratory (NSCL). The final array will consist of 24 plastic scintillator bars each with dimensions of 300 x 45 x 25 mm. The neutron energy will be determined by the time-of-flight technique, while the position of interaction will be deduced using the timing and energy information from photomultipliers attached to both ends of each bar. A prototype of the final array has been constructed and characterized in a simple test setup. Results of test measurements and simulations have demonstrated a neutron energy threshold of <130 keV and overall time (position) resolution of ≤1 ns (∼4 cm). [ABSTRACT FROM AUTHOR]

The mirror nuclei 25Mg and 25A1 are expected to have very similar structures. The Gamow-Teller (GT) transitions from the J&b.pi; = 5/2+ ground state of 25Mg to the excited states in 25A1 were studied by high-resolution measurements of the 25Mg(3He, t) charge-exchange reaction at 0° and at 140 MeV/nucleon. Assuming the usual J&b.pi; = 1+ selection rule for the spin-isospin-type GT transitions, the states with J&b.pi; = 3/2+, 5/2+, and 7/2+ should be excited. However, of the more than ten states with these J&b.pi; values below 6 MeV excitation energy, only the 5/2+ ground state and the 7/2+, 1.613 MeV state in 25A1 were strongly populated, while all other states were strongly suppressed. The analysis of Mi transitions in 25Mg also suggested a very similar feature for the analogous Mi transitions. Both 25Mg and 25A1 are known to be largely deformed, and most low-lying states can be interpreted in terms of one-particle quantum numbers in the deformed potential and the associated rotational spectra. The observed suppression can be explained in terms of the K quantum number selection rules that are inherent to axially deformed nuclei. [ABSTRACT FROM AUTHOR]

Studying the Gamow-Teller (GT) transitions of stable as well as unstable pf-shell nuclei is one of the key issues in nuclear and astro-nuclear physics. Under the assumption that isospin T is a good quantum number, symmetry is expected for mirror nuclei and the GT transitions starting from the mirror nuclei. We study the GT transitions starting from Tz = ±1 mirror nuclei, respectively, by means of hadronic (3He, t) charge-exchange reactions and complementary β decays. [ABSTRACT FROM AUTHOR]