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The high-spin states of 80 Y have been studied with the reactions 24 Mg( 58 Ni, pn γ ) at 180 MeV and 58 Ni( 24 Mg, pn γ ) at 77 MeV. Gamma-ray transitions in this nucleus have been unambiguously assigned by using the GASP detector array in conjunction with the recoil mass spectrometer CAMEL and the ISIS Silicon detector ball. These transitions have been arranged into several rotational bands extending up to an excitation energy of about 12 MeV and spin 24 ℏ. The bands are discussed within the framework of the interacting boson–fermion–fermion and cranked shell models.

For the investigation of the collectivity and the structure of the intruder bands with positive and negative parity in 114 Sn, coincidence lifetime measurements using the recoil distance Doppler shift (RDDS) and the Doppler-shift attenuation (DSA) methods were performed at the GASP spectrometer at the INFN-Laboratori in Legnaro. Excited nuclear states were populated with the reaction 100 Mo( 18 O,4n) 114 Sn. For analysis the differential decay curve method was used in the γγ -coincidence mode. In total 31 lifetimes could be obtained, belonging to 11 and 13 states in the positive- and negative-parity intruder bands, respectively, and to 7 spherical states. This work enhances our knowledge of low-lying collectivity among the Sn isotopes near the mid-shell region.

The first identification of gamma-rays from excited states of the 85 Mo and 88 Ru nuclei is reported, together with a short discussion of the evolution of the nuclear structure along the N = Z and the N = 43, 44 lines.

Transitions linking the highly deformed (HD) bands to states of normal deformation in 137 Sm and 139 Gd have been identified in experiments performed at GASP. The spins deduced for the HD bands in these N = 75 isotones support the previously assigned νi 13 2 [660] 1 2 + configuration. The different decay-out patterns of the two otherwise similar HD bands are tentatively explained by the difference in pairing between the Z = 62 and Z = 64 proton systems.

Rotational structures in 132Nd have been investigated via the 104 Pd ( 32 S ,2p2n) reaction at 160 MeV. Four highly-deformed bands have been observed, out of which three have been linked to the normal-deformed states. Two of them are signature partners. A mixing at high spin is observed between levels of one highly-deformed band and the ground-state band allowing for an unambiguous assignment of the spins and parity of that band. The present data brings new evidence on the role of the N = 72 shell gap to the stabilization of the highly-deformed minimum in the A = 130 mass region and on the importance of the νi 13 2 intruder orbital in the structure of the highly-deformed bands.

High-spin states in 43Ca, 45Sc, and 45Ti were studied with the GASP multidetector array coupled with the Recoil Mass Spectrometer. The nuclei were excited in the 60 MeV 18O +30Si reaction. Lifetimes were extracted from the analysis of the Doppler-shift attenuation of γ-rays observed in the reversed 35Cl+12C reaction. The lifetimes, B(M1) and B(E2) values for 45Sc are presented. The measurements suggest significant deformation of the positive-parity intruder band in this nucleus. The band is predicted by the mean-field calculations to be the cross-shell particle-hole excitation associated with a strong quadrupole core-polarization. Spherical shell-model calculations reproduce observed excitation energies and transition rates in both spherical and deformed structures.

High-spin states in the doubly odd nucleus Br-76 have been investigated using the Mn-55(Si-30,2 alpha n) reaction at a beam energy of 130 MeV. Five bands have been established to high spin. The features of the level scheme, particularly the signature inversion and the band crossings in the yrast band as well as proton and neutron alignments in the negative-parity bands, are discussed in the framework of the cranked shell model. (C) 1997 Elsevier Science B.V.