[en] Experimental studies of excited states in exotic nuclei populated by direct reactions using secondary RI beam are discussed from the aspects of the inverse kinematics and the selectivity of secondary reactions. Recent studies of γ-ray spectroscopy of low-lying states in N = 8 nucleus ¹²Be, which reveals disappearance of the p and sd-shell gap, are presented. For a high-resolution γ-ray spectroscopy, a new array consisting of segmented Ge detectors is developed by CNS. Specifications and preliminary experimental results are introduced

No abstract available

[en] For in-beam nuclear spectroscopy of projectile-like nuclei produced by nuclear reactions, we constructed an array of segmented planar-type Ge detectors at CNS, the University of Tokyo, which is capable for Doppler-shift correction of γ-rays by using position sensitivities in the detectors. The position sensitivity of the segmented planar-type Ge detector is based on pulse shapes from detectors. A method of pulse shape analysis by using an analog technique for extracting position information is discussed. Overall performance of the array is demonstrated based on recent results of an in-beam spectroscopy experiment

[en] In-beam spectroscopy of exotic nuclei using direct reactions is discussed from the aspects of the inverse kinematics by measuring in-flight decay of the beam-like nucleus and the selectivity of secondary reactions. For studies of unbound excited states invariant mass spectroscopy is discussed. For bound state, in-beam γ-ray spectroscopy of fast moving exotic nuclei has been giving interesting information of excitation spectra. Recent studies of neutron-rich Be isotopes are presented. For the next phase of the γ-ray spectroscopy, a new array consisting of high-resolution segmented Ge detectors is developed by CNS. Specifications of the array and the first experimental result are introduced.

[en] Coulomb dissociation reactions and E1 responses of halo nuclei, ¹¹Be and ¹¹Li, are discussed. The observed excitation energy spectra show prominent peaks around 1 MeV excitation with a large tail towards higher excitation energies, which can be explained by a direct Coulomb breakup mechanism to continuum states. In the case of the ¹¹Li nucleus having two halo-neutrons, the correlation between the neutrons in the ground state is discussed. (author). 21 refs., 3 figs

[en] Measurements of the interaction cross sections and a coincidence measurement of the Coulomb dissociation reaction of the neutron drip-line nuclei are presented. The density distribution of the ¹¹Li nuclei are deduced from the observed interaction cross sections on light targets at the intermediate energy region. Large E1 strength at the low excitation energy region is deduced for ¹¹Li from the analysis of the energy dependence of the Coulomb dissociation cross sections on heavy targets. The coincidence measurement (⁹Li + 2n) of the Coulomb dissociation reaction of the ¹¹Li nucleus gives the excitation energy spectrum of the E1 strength. The shape of the spectrum and the correlation of the two neutrons are discussed for the structure of the ¹¹Li nucleus. (author). 21 refs., 6 figs

[en] A problem lingers as to which of the two mechanisms is more responsible for ¹¹Li Coulomb dissociation. Moreover, ¹¹Li is particular as it possesses two halo neutrons. An intriguing problem emerges about how the dissociation is affected by the properties of the two neutron correlation. In order to elucidate these problems, the exclusive measurement of Pb(¹¹Li, ⁹Li+2n) reaction at the incident energy of 43A MeV was performed. The three particles, ⁹Li+2n, were measured simultaneously to obtain variety of the correlation spectra. The experiment was performed by using an unstable nuclear beam of ¹¹Li provided by the RIPS facility in RIKEN to irradiate a lead target. The excitation energy spectrum of the three-body system after the correction for the detection efficiency is shown and examined. Also the spectra of the component energies of the excitation energy of the whole three-body system (¹¹Li) are shown. It was indicated that the dissociation is due to the direct Coulomb breakup process leading to ⁹Li and di-neutron cluster. The attempt to explicitly treat the n-n motion has been done, and it is explained. (K.I.)

[en] The relation between nuclear density distribution and interaction cross section is discussed in terms of Glauber model. Based on the model, density distribution of neutron drip-line nucleus ¹¹Be and ¹¹Li is determined experimentally from incident energy dependence of interaction cross sections of ¹¹Be and ¹¹Li on light targets. The obtained distributions have long tails corresponding to neutron halos of loosely bound neutrons. (Author)

No abstract available

[en] CNS germanium detector array is introduced, which is dedicated for high-resolution γ ray spectroscopy of fast moving exotic nuclei produced in intermediate-energy direct reactions of unstable nuclear beam. (author)