T. Hayakawa

Rotational bands in115Sb

High-spin states of115Sb were studied by inbeamγ-ray spectroscopy using the89Y (29Si, 2pn) fusionevaporation reaction at a beam energy of 108 MeV. The experiments includedγ-γ coincidence and directional correlation of oriented nuclei (DCO) ratio measurements using six BGO Compton suppressed Ge detectors. An intruderΔJ=2 rotational band has been identified for the first time and it is interpreted as the h11/2 proton coupled to a two particle-two hole (2p − 2h) deformed state of the114Sn core. A ΔJ=1 rotational band based on the 2p − 1h, π{g72/2⊗g92/−1}, configuration has been extended to the 29/2+ state at an excitation energy of 5241 keV.

Signature dependence in the high spin states of128La

High spin states of128La have been investigated by means ofγ ray spectroscopy. Although two level schemes were reported prior to the present study, those schemes were different at excitation energies near the band head. A new level scheme has been obtained for the detailed discussion of signature dependence.

Collective and quasiparticle excitations in 128Ce

Abstract The level structure of the nucleus 128 Ce has been investigated via the 103 Rh( 28 Si,p2n) reaction at a beam energy of 105 MeV. Six new bands have been found. Spin and parity of levels are assigned based on γ-ray angular distribution and angular correlation measurements. The properties of collective and quasiparticle excitations of 128 Ce are investigated. A ν(h 11 2 ) 2 S-band is proposed and the crossing frequency is found similar to that for 126 Ba. The decoupled and semi-decoupled structures are discussed for the four negative-parity two-quasiproton bands. From an analysis of (g K − g R ) Q 0 ratios, the νh 11 2 (d 5 2 , g 7 2 ) configuration is proposed for a strongly coupled band structure.

High-spin states of odd-odd156Ho

High spin states in the nucleus156Ho have been studied via the fusion-evaporation reaction140Ce(19F,3nγ)156Ho at the beam energy of 82 MeV.γ-γ coincidences, Eγ, Iγ and excitation functions have been measured. With two rotationally-aligned bands identified as π[h11/2]ν [i13/2], we found two new bands with a signature splitting, whose structure is believed to arise from either ν[h9/2] or ν[f7/2] coupled to π[h11/2]. Our placement of γ rays belonging to these new bands suggests that the previously known level scheme should be corrected. We also found many new low-energy γ rays in the low excitation energy. As compared to154Ho, the present nucleus with two more neutrons becomes more collective, and shows well-observed rotationally-aligned bands with a clear signature splitting.

Level structure of 78 Rb

The excited states of78Rb have been investigated by means of in-beam andβ-γ spectroscopy. The production of78Rb and theβ radioactivity of78Sr have been made through the54Fe(28Si,3pn) and54Fe(28Si,2p2n) reactions, respectively. Four rotational bands have been observed in the high-spin band structure. The signature splitting is large in the two bands, while the other two bands have small splitting. A detailed low-lying level scheme of78Rb has been constructed for the first time via theβ decay of78Sr in order to search for a linking transition between the high-spin band head and low lying states.

ray spectroscopic study of128Ce

The level structure of the nucleus128Ce has been investigated via the103Rh(28Si, p2n) reaction at a beam energy of 105Me V. Six new bands have been found. The properties of the quasiparticle configuration for some new bands and the collective behaviours of128Ce are shortly discussed.

High spin states in115Te

High spin states in115Te have been studied using the89Y (29Si, p2n) reaction at a beam energy of 108 MeV.γ-γ coincidence, Eγ, Iγ and excitation functions have been measured. The level scheme has been extended to 82 MeV excitation energy relative to the 11/2 state and several new states are established. The systematical behaviour in odd- N Te isotopes is discussed.

Level structure of doubly odd154Ho

Abstract154Ho was studied via141Pr(16O,3n) reaction at beam energy of 75 MeV. We found two new rotationally aligned bands made of neutron h9/2 and f7/2 orbitals coupled to a proton h11/2 orbital. As with several new high-spin states, up to I=20, the ground state band with odd parity starts to show anomalous signature splitting at I=13 in this doubly odd154Ho. The observed rotational bands in154Ho are quite consistent with the onset of collectivity which appears in general at neutron number of 87 in neutron-deficient rare-earth nuclei.