Zs. Podolyák

Double and triple octupole excitations in the A≈150 region

The results of recent experiments performed at L.N.L. on multiple octupole excitations in the N=84 isotones are reviewed. In particular, the results on B(E3) strengths in 146Sm are discussed and expectations for higher-order octupole excitations are compared with the present experimental situation.

HIGH SPIN STATES POPULATED VIA PROJECTILE FRAGMENTATION IN VERY NEUTRON-RICH NUCLEI AROUND MASS 180

K-isomers can be found mainly in the A∼180 region. The best examples of K-isomerism are predicted to occur on the neutron-rich side of the valley of stability and are thus barely reachable by standard nuclear reactions like deep inelastic reactions. Up to now, only projectile fragmentation has proven to be an efficient method in populating heavy neutron-rich isotopes with cross-sections sufficient to perform γ-ray spectroscopy. Thus, the FRagment Separator [1] (FRS) associated with γ-ray spectroscopy techniques has been successfully used at GSI to search for K-isomers with lifetimes ranging from nanoto milliseconds in the mass region around A∼180.

MARS - A NOVEL γ-RAY DETECTOR ARRAY

MARS Mini ARray of Segmented detectors is the Italian effort to explore the feasibility of building a high performance 4π array for γ-ray spectroscopy based on γ-ray tracking. The most advanced present arrays, EUROBALL and GAMMASPHERE, are built of Compton suppressed HPGe spectrometers arranged in tightly packed spherical configurations. Despite the fact that these arrays are already composed of more than 100 detectors, their performance is limited to an efficiency of only about 10% and a response function (P/T-ratio) with about 60% of the total intensity in the full energy peak at 1 MeV. The good P/Tratio is achieved rejecting the signal from the detector when the surrounding BGO shield detects γ-rays Compton scattered out of the Ge crystal. However, the use of the suppression shields prevents to cover more than one half of the solid angle with Ge detectors limiting the achievable efficiency considerably to the present values. It is an established fact that an array with better performance cannot be obtained by simply increasing the number of detectors.

High spin studies of 64Gewith EUROBALL

The high-spin states of the N=Z nucleus 64Ge have been investigated using the EUROBALL array coupled to the ISIS Si-ball and to a highly efficient n-Wall. Spins and parities were assigned on the basis of a DCO and of a polarization analysis.

Decay out of the highly-deformed bands in the A=130 mass region and experimental Δν for Nd nuclei

A review of the results on the decay out of highly-deformed bands in the A=130 mass region is presented, including new experimental information on the decay out of two highly-deformed bands in 132Nd and 134Nd. The previously observed E2 linking transitions are explained by the crossing with observed nonyrast bands of normal deformation. Large interaction matrix elements and mixing amplitudes between the interacting highly-deformed and normal-deformed bands are deduced. The large normal-deformed admixture into the lowest observed highly-deformed states explains why the decay out occurs at a certain spin along the band and shows that the barrier between the highly-deformed and normal-deformed minima disappears at low spins. Results on the decay out of the highly-deformed band of 136Nd are reported and the extraction of Δν for the highly-deformed Nd nuclei is discussed.