[en] A search for octupole deformation in neutron rich Xe isotopes has been conducted through gamma-ray spectroscopy of primary fragments produced in the spontaneous fission of ²⁴⁸Cm. The spectrometer consisted of the Eurogam array and a set of 5 LEPS detectors. Level schemes were constructed for Xe isotopes with masses ranging from 138 to 144. Except for ¹³⁹Xe, none of them exhibit an alternating parity quasimolecular band, α feature usually encountered in octupole deformed nuclei. Substantial evidence for reflection asymmetric shape in the intrinsic system of the nucleus exists for the light actinide nuclei

[en] Excited levels of ¹⁴¹Xe, populated in spontaneous fission of ²⁴⁸Cm, were studied by means of prompt γ-ray spectroscopy, using the EUROGAMM2 array. Level scheme of ¹⁴¹Xe obtained in this work shows patterns characteristic of simplex symmetry with s = +i and s = -i bands present but low value of D₀ moment indicates that octupole correlations in Xe isotopes are systematically lower than in Ba nuclei.

[en] Neutron-rich nuclei ^147,149,151Ce have been studied via the prompt γ-ray spectroscopy of ²⁴⁸Cm fission fragments. A partial level scheme for ¹⁵¹Ce is presented for the first time, along with the high-spin structure in ^147,149Ce. A rapidly changing yrast structure with neutron number is observed and it is suggested that bands in ¹⁴⁷Ce and ¹⁵¹Ce are built on the νi_13/2 Nilsson state. The level scheme of ¹⁴⁹Ce displays two bands with quite similar transition energies. There is no experimental evidence for octupole deformation in any of the three nuclei. copyright 1997 The American Physical Society

[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] 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] In heavy ion collisions at near relativistic energies, electromagnetic excitation of the double giant dipole resonance occurs with large cross sections. We summarize the presently available experimental data and discuss related theoretical efforts. Emphasis is paid to the question of anharmonicities and to the damping of the two-phonon states

[en] A γ-γ coincidence technique has been developed for g-factor measurements of short-lived nuclear states. The method involves γ-detection in 4π geometry as well as transient magnetic fields and the recoil-distance technique. A first experiment was performed for the isotope ¹⁶⁰Yb produced in the reaction ⁶⁴Ni(¹⁰⁰Mo,4n) at 430 MeV beam energy. The negative g-factor, g=-0.18±_0.29^0.26, of the 14⁺ yrast state establishes the νi_13/2 quasiparticle structure to be responsible for the first backbend. Mean g-factors for spins above and below the 14⁺ state were also derived as well as lifetimes for yrast states up to 1^π = 18⁺. (orig.)

[en] A γ-γ coincidence technique has been developed for g-factor measurements of short-lived nuclear states. The method involves γ-detection in 4π geometry as well as transient magnetic fields and the recoil-distance technique. A first experiment was performed for the isotope ¹⁶⁰Yb produced in the reaction ⁶⁴Ni(¹⁰⁰Mo, 4n) at 430 MeV beam energy. The value g=-0.23(31) of the 14⁺ yrast state, which is compatible with zero, establishes the νi_13/2 quasiparticle structure to be responsible for the first backbend. A mean g-factor for low spin states around the 4⁺ state, g=+0.48(26) was also derived as well as lifetimes for yrast states up to I^π=18⁺. (orig.)

[en] Nucleon transfer accompanied by Coulomb excitation was studied in the system ^2O6Pb + ²³²Th at E_Lab =6.4 MeV/u. Particle -particle-gamma coincidence techniques were used to identify excited states of reaction products populated through inelastic scattering and nucleon transfer reactions. The mean excitation energy was measured by means of a γ-ray energy and multiplicity filter consisting of 6 NaI detectors. Large cross sections for one neutron and two-neutron pick-up from ²³²Th are observed. The impact-parameter dependence of the neutron transfer is analyzed in terms of semiclassical barrier penetration models. Using realistic neutron potentials with a diffuse surface, the experimental data are in accordance with the assumption of a 'cold' transfer to states near the yrast line. (orig.)

[en] Published in summary form only