Reaction cross sections of Li-8 on stable targets were measured at intermediate energies. With the existing experimental data of interaction cross sections at 790 MeV/nucleon the nucleon density distribution of Li-8 was extracted by the use of the modified Glauber model. Meanwhile, the existing data of B-8 have been also reanalyzed. Structures of Li-8 and B-8 were compared through the density. On the basis of dilute surface densities, the discussion of Li-7(n,gamma) Li-8 and Be-7(p,gamma) B-8 capture reactions was performed within the framework of the direct capture reaction mechanism. The calculations agreed quite well with the experimental data as well as other analyses.

The total charge-changing, charge pick-up, and partial charge-changing cross sections of very neutron-rich nuclei (Ne-30, Na-32,Na-33) with a proton target have been measured at similar to 240A MeV for the first time. We introduced the phenomenological correction factor in Glauber-model calculations for the total charge-changing cross sections with the proton target, and applied it to deduce the proton radii of these nuclei. For 30Ne and Na-32, the neutron skin thicknesses of the nuclei were deduced by comparing the proton radii with the matter radii deduced from the interaction cross-section measurements. A significant thick neutron-skin has been observed for the nuclei. We also found that the charge pick-up cross sections are much larger than those in the systematics of stable nuclei.

We have precisely measured reaction cross sections (sigma(R)) for Li-8 using Be-9, C-12, Al-27, and proton targets at intermediate energies by the transmission method. From the energy dependence of the sigma(R) including the high energy data, the density distribution of Li-8 was deduced through a modified Glauber model. It is shown that Li-8 has a shorter tail structure in the density as compared with that of B-8 and the matter radius of Li-8 is similar to those of the other nonhalo Li isotopes. The result is consistent with the previous experiments that there is a tendency for Li-8 to be a skin nucleus.

We measured the reaction cross sections of the two-neutron halo nucleus 14Be with proton and carbon targets at about 41 and 76 MeV/nucleon. Based on a Glauber model calculation, we deduced the matter density distribution of 14Be in which previously measured interaction cross sections at relativistic energies were also included. An s-wave dominance in 14Be has been confirmed, although the halo tail of 14Be is not distributed as much as that of 11Li. Significant mixing of the p-wave in addition to the s- and d-wave is also suggested.

The question of whether charge-changing interactions can be used to probe point-proton radii of nuclei remains unanswered. Charge-changing cross sections, sigma(cc), were systematically investigated using stable and unstable nuclear beams of intermediate-energy. The ratios of the experimental sigma(cc) values to the calculated ones obtained from a phenomenological Glauber-type model analysis are found to be nearly constant in a broad range of Z/N for light neutron-rich nuclei. This enables the determination of density distributions, i.e., the radii of protons tightly bound in nuclei. To test the applicability of the present method to all nuclei in the nuclear chart, extensive measurements were performed for medium-mass nuclei ranging from Z = 18 to 32. The present study suggests the potential capability of a new experimental approach for exploring exotic nuclei.

We measured the reaction cross sections of the two-neutron halo nucleus Li-11 with solid hydrogen and carbon targets at around 31 and 41 MeV/nucleon. The neutron density distribution of Li-11 was deduced for the first time by the Glauber model calculation based on the optical limit approximation. The uncertainty of the matter density of Li-11 was improved, compared with earlier measurements. The present root-mean-square radius of the proton distribution agrees with the previous one derived from an optical isotope shift measurement. The present root-mean-square radii reproduce theoretical calculations by the tensor optimized shell model by assuming core excitation. This consistency suggests the possibility that Li-9 in Li-11 is excited and the disappearance of the N = 8 shell gap of Li-11 is caused by correlations originating from the nucleon force, such as the tensor and the pairing.

The half-lives of fully ionized and hydrogen-like (H-like) 122I ions have been measured in a heavy-ion storage ring. The \( \beta^{+}_{}\) -decay constants for both charge states and the electron capture (EC) decay constant of H-like ions have been determined. The EC-decay constant in H-like 122I ions \(\ensuremath \lambda^{\text{H-like}}_{\rm EC}=7.35(33)\cdot10^{-4}{\,\mbox{s}}^{-1}\) is, within the uncertainty, the same as the one in neutral atoms. This result is in agreement with the estimates of recent theoretical considerations on the EC-decay of few-electron ions that explicitly take into account the conservation of the total angular momentum of the nucleus plus lepton(s) system and its projections. No firm confirmation could be concluded from our results on the predicted effect that allowed Gamow-Teller transitions become forbidden if the initial and final total angular momenta are not equal.-1

A search for isomeric gamma-decays among fission fragments from 345 MeV/nucleon 238U has been performed at the RIKEN Nishina Center RI Beam Factory. Fission fragments were selected and identified using the superconducting in-flight separator BigRIPS and were implanted in an aluminum stopper. Delayed gamma-rays were detected using three clover-type high-purity germanium detectors located at the focal plane within a time window of 20 microseconds following the implantation. We identified a total of 54 microsecond isomers with half-lives of ~0.1 - 10 microseconds, including discovery of 18 new isomers in very neutron-rich nuclei: 59Tim, 90Asm, 92Sem, 93Sem, 94Brm, 95Brm, 96Brm, 97Rbm, 108Nbm, 109Mom, 117Rum, 119Rum, 120Rhm, 122Rhm, 121Pdm, 124Pdm, 124Agm and 126Agm, and obtained a wealth of spectroscopic information such as half-lives, gamma-ray energies, gamma-ray relative intensities and gamma-gamma coincidences over a wide range of neutron-rich exotic nuclei. Proposed level schemes are presented for 59Tim, 82Gam, 92Brm, 94Brm, 95Brm, 97Rbm, 98Rbm, 108Nbm, 108Zrm, 109Mom, 117Rum, 119Rum, 120Rhm, 122Rhm, 121Pdm, 124Agm and 125Agm, based on the obtained spectroscopic information and the systematics in neighboring nuclei. Nature of the nuclear isomerism is discussed in relation to evolution of nuclear structure.

Interaction cross sections (σI) for Ne isotopes from the stability line to the vicinity of the neutron drip line have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN. The σI for 27–32Ne in every case exceed the systematic mass-number dependence of σI for stable nuclei, which can be explained by considering the nuclear deformation. In particular the σI for 29Ne and 31Ne are significantly greater than those of their neighboring nuclides. These enhancements of σI for 29Ne and 31Ne cannot be explained by a single-particle model calculation under the assumption that the valence neutron of 29Ne (31Ne) occupies the 0d3/2 (0f7/2) orbital, as expected from the standard spherical shell ordering. The present data suggest an s dominant halo structure of 29Ne and s- or p-orbital halo in 31Ne.

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

Charge-changing cross sections σ(cc) of stable and unstable nuclei ((9-11)Be, (14-16)C, and (16-18)O) on a carbon target were investigated at 300  MeV/nucleon. A phenomenological analysis based on the Glauber theory indicates an approximate, but universal, scaling of σ(cc) over a wide range of A/Z. This allows the determination of the density distributions of protons tightly bound in the nuclei. An application to (16)C, which is considered to be an anomalously deformed nucleus, indicates a systematic evolution of proton root-mean-square radii and has revealed for the first time a neutron skin effect in carbon isotopes. Being complementary to isotope-shift and electron-scattering experiments, the present method can open up a new approach to explore the structure of exotic nuclei.

Interaction cross sections (sigma(I)) for Ne isotopes from the stability line to the vicinity of neutron-drip line have been measured using the RIBF facility at RIKEN. Measurements have been performed for Ne20-32 on C target at energies around 240 MeV/nucleon. A large enhancement of sigma(I) beyond the systematics of stable nuclei have been observed for neutron-rich Ne isotopes. The possible halo structures with lower orbital angular momentum for Ne-29,Ne-31 are discussed by the preliminary analysis.

Reaction cross sections (σR) for 11Be and 8B on proton targets at 50A∼120AMeV have been measured to distinguish between the proton- and neutron- density distributions at the nuclear surface. The σR is connected with the nucleon density distributions by the Glauber theory. Since the nucleon-nucleon total cross sections in that energy region have a large isospin dependence, the σR on proton targets should have a large difference between the proton and neutron in the halo structure. The experimental σR on proton targets are in good agreement with the calculated ones assuming that the tail dominantly consists of a neutron for 11Be and a proton for 8B.

Reaction cross sections for stable nuclei at intermediate energies have been measured precisely and systematically. The data have been found to be reproduced nicely by the optical‐limit approximation of Glauber theory modified to include the nucleon multiple scattering effect and the Fermi‐motion effect. Applying this prescription, the nucleon density distribution of 17Ne has been studied. The surface structure of 8B and 11Be has been also studied using this prescription and hydrogen targets. Using the RIBF that has just started application to studies of exotic nuclei, neutron‐rich Ne isotopes around the Island of Inversion have been investigated through measurements of their interaction cross sections.

Interaction cross sections have been measured for spin-aligned nuclear beams of deformed nucleus. The spin-aligned nuclear beams were created by selecting the momentum of fragments produced in the projectile fragmentation of intermediate energy heavy-ion beams. The directional correlation of nuclear reaction probability for heavy-ion beams of deformed nucleus has been directly observed for the first time.

The charge-changing cross sections (sigma(cc)) of Si-28 on a carbon target were measured with high precision at intermediate energies from 100 to 600 MeV/nucleon. The measured scc decreases rapidly from low energies up to 200 MeV/nucleon, whereas at higher energies it appears almost constant. The energy dependence of scc is compared with a Glauber-type model calculation where only the proton distribution of Si-28 is taken into account. A phenomenological correction factor deduced from the present data satisfactorily reproduces the experimental scc for other stable nuclei, whose charge distributions were determined by electron scattering and muon capture experiments.

The β-NMR study of short-lived nucleus 58Cu (I π  = 1 + , T 1/2 = 3.2 s) in Si has been performed. Spin polarization of 58Cu induced by the charge exchange reaction of 58Ni was observed in Si at 15 K. The 58Cu magnetic moment \(|\upmu[^{58}\mbox{Cu}]| = (0.46 \pm 0.03)\upmu_{\rm N}\) deduced from the β-NMR spectrum is consistent with the previous results on the laser spectroscopy. The present result shows that the 58Cu nucleus is promising as a new nuclear probe for the microscopic study of Cu impurities in Si.

We report on the first spectroscopic study of the N=22 nucleus 32Ne at the newly completed RIKEN Radioactive Ion Beam Factory. A single gamma-ray line with an energy of 722(9) keV was observed in both inelastic scattering of a 226 MeV/u 32Ne beam on a Carbon target and proton removal from 33Na at 245 MeV/u. This transition is assigned to the de-excitation of the first J^pi = 2+ state in 32Ne to the 0+ ground state. Interpreted through comparison with state-of-the-art shell model calculations, the low excitation energy demonstrates that the Island of Inversion extends to at least N=22 for the Ne isotopes.