No abstract available

[en] Yttrium-81 with very small fusion cross section was studied using NORDBALL in conjunction with very powerful filters for reaction channel selection. It was proved that Clean-up of γ - γ matrix is very useful to study ⁸¹Y nucleus. Ground state band show a rotational alignment of gq/2 neutrons at a rotational frequency of 0.68 MeV. This alignment is consistent with a neighbouring even-even nucleus of ⁸⁰Sr. (author)

[en] Isomer search for neutron-rich Cs isotopes was carried out to investigate the shape evolution as a function of neutron number. The experiment was performed as one of the EURICA campaign experiments using a "2"3"8U beam at RI Beam Factory, RIKEN Nishina Center. Isomers in "1"4"5Cs, "1"4"6Cs, "1"4"7Cs, and "1"4"8Cs were newly found. Decay schemes of isomers in "1"4"5Cs and "1"4"6Cs have been tentatively proposed. The isomer in "1"4"6Cs isotope is considered to be caused by the low-energy transition directly decay from the isomer. The isomer in the "1"4"5Cs isotope is proposed to be candidate of the K isomer. (author)

No abstract available

[en] In order to search for high-spin isomers in N=51 isotones, an unstable nuclear beam ¹⁷N was developed using the low-energy radioisotope beam separator (CRIB) of the Center for Nuclear Study (CNS), University of Tokyo, in RIKEN. High-spin isomers in N=83 isotones have been systematically studied. These isomers are of stretch coupled configurations and oblate shape. High-spin isomers of N=51 isotones are expected to be stemmed from the same isomerism appeared in N=83 isotones. Since the nuclei with Z < 40 of N=51 isotones are close to the stability line, it is difficult to produce high-spin states in these nuclei using reactions by combinations of stable beams and targets. Therefore, it is very effective to use the radioisotope beam. Experiment was carried out by means of the γ spectroscopy method, Seven γ-rays emitted from Nb nuclei which were produced by the secondary fusion reaction of ⁸²Se + ¹⁷N were observed. (author)

[en] The high-spin states of ⁹³Mo have been studied in ⁸²Se(¹⁶O, 5n)⁹³Mo reaction at a beam energy of 100 MeV using technique of in-beam γ spectroscopy. Measurements of γ-t, γ-γ-t coincidences, γ-ray angular distributions, and γ-ray linear polarizations were performed. The high-spin isomer was discovered at 9.7 MeV excited state. The near yrast states in ⁹³Mo were well described using the weak coupling picture of a d_5/2 neutron to a neutron magic core nucleus ⁹²Mo. (author)

[en] The nuclear g-factor of the T_1/2 = 28 ns high-spin isomer in ¹⁴⁹Dy has been measured using the γ-ray time-differential perturbed angular distribution (TDPAD) technique with a pulsed beam of ¹³²Xe. The experimental value g=+0.41(6) is in good agreement with a fully aligned multi-quasiparticle configuration π(h²_11/2)xν(f_7/2h_9/2i_13/2(d^-2_3/2)₀). This result indicates that only neutron particle-hole excitations across the N=82 shell-closure occur at this isomeric state

[en] We are developing a new neutron detector array to investigate the exotic structure of very neutron-rich nuclei. The detector was designed to measure the β-delayed neutrons in a wide energy range of 0.1-5 MeV with high energy resolution and high detection efficiency. In the present experiment, the performance of the single detector element was evaluated by using the well-known neutrons emitted after the β-decay of ¹⁷N, ¹⁶C, ¹⁸N produced with 180 MeV/u ¹⁸O beam. It was confirmed that the low energy neutrons were successfully detected with higher efficiency. (author)

[en] The neutron deficient isotope ⁷⁹Y has been firstly identified and the decay properties were studied from β-decay measurements in the reaction of ⁵⁴Fe(²⁸Si, p 2n) at 92 MeV. Three γ rays of 152.5, 177.4, and 1106 keV were observed concerning the β decay. The half life and Q_EC value were determined to be 14.9±0.6 s and 7.12±0.45 MeV, respectively. The decay scheme including spin-parity is discussed, and 5/2⁺ assignment for the ground state is proposed. (orig.)

[en] A recoil distance method was used to measure half-lives of the excited states of ¹⁴⁵Sm. The reaction used was ¹³⁹La(¹⁰B,4n)¹⁴⁵Sm. A plunger system was used. Half-lives were determined for two excited states for the first time. The yrast 27/2⁺ state was found to have a half-life of 1.1±0.2 ns corresponding to the retardation of 3.1 x 10^-4 comparing with the single particle estimate of M1. The excitation energy of this state was well reproduced by the shell model calculation having a mixed configuration of [π{h_11/2(g_7/2)^-2 (d_5/2)^-1}_10-,νf_7/2]+[π{h_11/2(g_7/2)^-1}_9-,νh_9/2]. Another retarded E1 transition was also found in a decay of a 21/2⁺ state. Its retardation was 1.6 x 10^-4 comparing with the single particle value. (orig.)