[en] Excited states in ¹³⁹Te were observed for the first time, using EUROGAM2 multidetector array to measure prompt-γ radiation following the spontaneous fission of ²⁴⁸Cm. The systematic behavior of excitation energies in the N=87 isotones and the multipolarity measurements suggest spin 7/2^- for the ground state and 9/2^- for the 271.0 keV level in ¹³⁹Te. The 271.0 keV level most likely corresponds to the νh_9/2 single-particle excitation. A shape transition from spherical to prolate Te isotopes is observed at the neutron number N=87, in accord with the Hartree-Fock plus BCS, PES calculations. Predictions for excitations in the ¹³⁷Sn nucleus are made based on the extended systematics obtained for the N=87 isotones

[en] Excited states in ¹²⁶Ce have been observed with the GAMMASPHERE γ-ray detector array, used in conjunction with the MICROBALL charged-particle detector. The reaction ⁶⁴Zn(⁶⁴Zn,xpnα) (beam energy 260 MeV) was used to populate a wide range of nuclei in the neutron-deficient region with A∼120. ¹²⁶Ce was populated via the 2p evaporation channel. The three previously observed bands have been extended to higher spins and some other structures have been identified. The yrast band shows evidence of a delayed neutron alignment occurring at a rotational frequency ω∼0.5 MeV/ℎ as observed in the neighboring odd-A nucleus ¹²⁷Pr. One of the two excited bands shows evidence for a similar crossing at a slightly lower frequency and also exhibits a sudden gain in alignment at ω=0.57 MeV/ℎ. The third band may involve the coupling of a γ-vibrational state. All three rotational bands are discussed in terms of standard and extended cranked shell model calculations

[en] Arrays of Anti-Compton Spectrometer enabled systematic investigations of octupole correlations in the neutron-rich lanthanides. The studies mostly confirm the theoretical expectations of moderate octupole deformation at medium spins in nuclei from this region but in some cases predictions deviate from the experiment. In cesium isotopes strong octupole effects are predicted but not observed and new measurements for ¹³⁹Xe suggest octupole effects stronger than expected. Systematics of excitation energy of the 31 states excitations, updated in the present work for Xe isotopes, indicates the N=85 and Z=54 lines as borders for strong octupole correlations. Systematic of electric dipole moment, upgraded in the present work for Ca and Ce isotopes confirms the Z=54 limit and adds new information about local canceling of electric dipole moment at the N=90 neutron number

[en] Prompt γ-ray cascades in neutron-rich nuclei around doubly magic ¹³²Sn have been studied at Eurogam II using a ²⁴⁸Cm fission source. Here we report results for the four-valence-proton N=82 nucleus ¹³⁶Xe and for its N=83 neighbor ¹³⁷Xe. For both nuclei, the yrast level spectra have been considerably extended, and empirical nucleon-nucleon interactions have been used to assign probable shell model configurations for most of the observed levels

[en] Excited states in the nucleus ¹³³Sb, populated in spontaneous fission of ²⁴⁸Cm, were studied with EUROGAM2. Medium-spin structure, described as the ν(f_7/2h_11/2^-1) multiplet of the ¹³²Sn core coupled to the odd proton in the g_7/2 orbital, has been identified in this nucleus. Levels corresponding to the octupole excitations of the ¹³²Sn core were also identified. Some uncertainties concerning isomeric decays in ¹³³Sb, observed in previous works, have been resolved. (c) 2000 The American Physical Society

[en] Excited states have been populated in ₅₂¹¹⁰Te via the ⁵⁸Ni(⁵⁸Ni,α2pγ) reaction at 250 MeV. The Gammasphere γ-ray spectrometer was augmented with ancillary detectors for charged-particle and neutron detection in order to provide clean channel selection. The known level scheme of ¹¹⁰Te has been greatly expanded with the addition of many new structures. Above spin 8⁺, negative-parity structures become yrast. The level scheme of ¹¹⁰Te below 30(ℎ/2π) is discussed in this paper, including possible evidence for octupole correlations inferred from strong B(E1) strengths

[en] Excited states in ¹³⁷Te, populated in spontaneous fission of ²⁴⁸Cm, were studied by means of prompt-γ spectroscopy, using the EUROGAM2 multidetector array. This is the first observation of excited states in ¹³⁷Te. The yrast excitations of ¹³⁷Te are due to the three valence neutrons, occupying the νf_7/2 and νh_9/2 orbitals, similarly as observed in its heavier N=85 isotones. Systematic comparison of excited levels in the N=85 isotones shows inconsistencies in spin and parity assignments in ¹³⁹Xe and ¹⁴¹Ba nuclei. The new data for ¹³⁷Te do not confirm earlier suggestions that octupole correlations increase in the N=85 isotones, close to the Z=50 closed shell. (c) 2000 The American Physical Society

[en] High-spin states have been populated in ₅₂¹¹⁰Te via ⁵⁸Ni(⁵⁸Ni,α2pγ) reactions at 240 and 250 MeV. The Gammasphere γ-ray spectrometer was used in conjunction with the Microball charged-particle detector. The high-spin (I>30) collective level scheme of ¹¹⁰Te, up to ∼45(ℎ/2π), is discussed in this paper. Four new decoupled (ΔI=2) high-spin structures have been observed for the first time, together with two strongly coupled (ΔI=1) bands. These bands all show the characteristics of smooth band termination, and are discussed within the framework of the cranked Nilsson-Strutinsky approach