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The highly-efficient and segmented TIGRESS y-ray spectrometer at TRIUMF has been used to perform a reorientation-effect Coulomb-excitation study of the 2+ state at 3.368 MeV in l0Be. This is the first Coulomb-excitation measurement that enables one to obtain information on diagonal matrix elements for such a high-lying first excited state from y-ray data. With the availability of accurate lifetime data, a value of --0.110 ± 0.087 eb is determined for the 〈2+1||Ê2||2+1|〉 diagonal matrix element, which assuming the rotor model, leads to a negative spectroscopic quadrupole moment of Qs(2+1) = --0.083 ± 0.066 eb. This result is in agreement with both no-core shell-model calculations performed in this work with the CD-Bonn 2000 two-nucleon potential and large shell-model spaces, and Green's function Monte Carlo predictions with two- plus three-nucleon potentials. [ABSTRACT FROM AUTHOR]

Background: Nuclei in the A " 190 mass region show gradual shape changes from prolate through nonaxial deformed shapes and ultimately towards spherical shapes as the Pb region is approached. Exploring how this shape evolution occurs will help us understand the evolution of collectivity in this region. Purpose: The level scheme of the 192 Au nucleus in A "190 region was studied in order to deduce its deformations. Methods: High-spin states of 192Au have been populated in the 186W("B, 5n) reaction at a beam energy of 68 MeV and their ? decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory (WNSL), Yale University. Results: Based on double and triple ?-ray coincidence data the level scheme of 192 Au has been extended up to Ip = 32+ at an excitation energy of ~6 MeV. Conclusion: The results are discussed in the framework of pairing and deformation self-consistent total Routhian surface (TRS) and cranked shell model (CSM) calculations. The comparison of the experimental observations with the calculations indicates that this nucleus takes a nonaxial shape similar to other Au nuclei in this region. [ABSTRACT FROM AUTHOR]

High-spin properties of the nucleus 117Hf were studied through the 128Te(48Ca,5n) reaction. Previously known bands have been extended to significantly higher spins and four new bands have been extracted from these data. The results are discussed within the framework of the cranked shell model aided by a comparison with level structures in the neighboring nuclei. The band crossings at rotational frequencies ∼500 keV are interpreted as caused by the alignments of h11/2 and h9/2 proton Orbitals. Band ED2 exhibits an alignment pattern similar to that of band EDI which was reported in a recent paper and proposed to be built on a second potential energy minimum involving the deformation-driving proton i13/2 ⊗ h19/2 configuration. It is likely that band ED2 is also associated with a deformation enhanced with respect to that of the normal deformed structures. Further experimental investigation is needed to ascertain the nature of this band. [ABSTRACT FROM AUTHOR]

A high-precision branching-ratio measurement for the superallowed ß+ emitter 26Alm was performed at the TRIUMF-ISAC radioactive ion beam facility. An upper limit of <12 ppm at 90% confidence level was found for the second forbidden yS+ decay of 26Alm to the 2 state at 1809 keV in 26Mg. An inclusive upper limit of 15 ppm at 90% confidence level was found when considering all possible nonanalog jö+/EC decay branches of 26 Alm, resulting in a superallowed branching ratio of 100.0000+0-0.0015 %. [ABSTRACT FROM AUTHOR]