T. Minemura

Quadrupole deformation of 12Be studied by proton inelastic scattering

Abstract Inelastic proton scattering exciting the 2 + 1 states in the neutron-rich beryllium isotopes 10,12 Be has been studied in inverse kinematics. From a coupled-channel analysis, the deformation lengths for the 2 + 1 states in 10 Be and 12 Be were determined to be 1.80±0.25 fm and 2.00±0.23 fm respectively, indicating that a tendency towards strong quadrupole deformation is preserved for these nuclei and that the singly-closed shell structure does not prevail in 12 Be. A quantitative analysis based on shell model calculations supports this picture.

Isomeric 0+ state in 12Be

An isomeric 0+ state at E x = 2.24 MeV in 12Be was found in the projectile fragmentation of 18O at 100 A MeV on a Be target. The excitation energy and the spin assignment were deduced by the measurements of the energies and the angular correlation function of the coincident two γ-rays corresponding to the 0+ → 2+ → 0+ decay, respectively.

Coulomb excitation of 56Ni

We have performed an experiment of Coulomb excitation of a doubly magic nucleus 56Ni to its first excited 2+ state at 2.7 MeV in inverse kinematics. Radioactive 56Ni particles at an incident energy 70.7 MeV/nucleon with 1500 s−1 was obtained via fragmentation of 58Ni at RIPS facility of RIKEN. The E2 transition probability B(E2) between the 0+ ground state to the first 2+ state was deduced to be 580±70 e2fm4 by a coupled channel analysis assuming Coulomb excitation mechanism. The present result agrees with the value deduced from the 56Ni+p inelastic scattering experiment at GSI.

Coulomb dissociation of 12N and 13O

The Coulomb breakup technique was applied to determine the E1 strength of excited levels in 12N and 13O, which dominate the low-energy cross sections of the 11C(p,γ)12N and 12N(p,γ)13O reactions, respectively. These reactions are important in the hot pp mode nuclear burning in hydrogen-rich massive objects [1]. Under a high-temperature and high-density condition, these capture reactions become faster than the β + decay of 11C and 12N. However, these 11C(p,γ)12N and 12N(p,γ)13O reactions are difficult to study experimentally because the life times of 11C and 12N are too short to prepare them as targets.

Deformation of the neutron-rich isotope 34Mg studied via in-beam gamma-ray spectroscopy using two-step fragmentation

Low-lying excited states in the very neutron-rich isotope 34Mg were studied via in-beam gamma-ray spectroscopy using a two-step fragmentation reaction. The excited 34Mg nuclei were produced by the projectile fragmentation reaction of a radioactive 36Si beam on a 386 mg/cm2 9Be target at 38 MeV/nucleon. De-excitation gamma rays were detected in coincidence with the reaction products. Two gamma lines associated with 34Mg were observed at 660(10) keV and 1460(20) keV, which are tentatively assigned to the 21+→0g.s.+ and 41+→21+ transitions in 34Mg, respectively. These assignments result in a very low energy of the 21+ state and a E(41+)/E(21+) ratio of about 3.2, suggesting large deformation of 34Mg.