Search

It was shown that the evolution of the B(E2; 2+1 0+1) values in N = 80 isotones from Te to Nd is affected by the underlying subshell structure. This manifests itself in the observation of the local suppression of the B(E2) value at Z = 58 with respect to the neighboring nuclei 136Ba and l40Nd. To investigate this shell sensitivity toward the Z = 64 subshell gap, the fi(E2+1 → 0+1) value of the unstable nucleus l42Sm was measured utilizing the projectile Coulomb excitation technique. The radioactive ion beam (RIB) experiment was performed at the REX-ISOLDE facility at CERN. The B(E2) value of 32 (4) W.u. reflects the impact of the πr(1g7/22d5/2) subshell closure at Z = 64 with respect to a linear scaling of collectivity with valence proton number. [ABSTRACT FROM AUTHOR]

Background: Recent data on N = 80 isotones have suggested that the proton π(1g7/2) subshell closure at Z = 58 has an impact on the properties of low-lying collective states. Purpose: Knowledge of the B(E2;21+ → O1+) value of 140Nd is needed in order to test this conjecture. Method: The unstable, neutron-rich nucleus 140Nd was investigated via projectile Coulomb excitation at the REX-ISOLDE facility with the MINIBALL spectrometer. Results: The B(E2) value of 33(2) W.u. expands the N = 80 systematics beyond the Z = 58 subshell closure. Conclusions: The measurement demonstrates that the reduced collectivity of 138Ce is a local effect possibly due to the Z = 58 subshell closure and requests refined theoretical calculations. The latter predict a smoothly increasing trend. [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]

Post-accelerated isomerically purified radioactive beams, available at the CERN On-Line Isotope Mass Separator facility using the resonant ionization laser technique, have been used to study the Coulomb excitation of the Iπ = 3- state in 70Cu (Z = 29, N = 41). While first results using a Iπ =6- beam were reported previously, the present complementary experiment allows us to complete the study of the multiplet of states (3-, 4- ,5-,6-) arising from the π2p3νlg9/2 configuration. Besides the known γ-ray transition deexciting the 4- state, a ground-state γ ray of 511(3) keV was observed for the first time and was unambiguously associated with the 5- state deexcitation. This observation fixes the energy, spin, and parity of this state, completing the low-energy level scheme of 70Cu. B(E2) values for all possible E2 transitions within the multiplet were determined. A comparison with large-scale shell model calculations using different interactions and valence spaces shows the importance of proton excitation across the Z = 28 shell gap and the role of the 2d5/2 neutron orbital. [ABSTRACT FROM AUTHOR]

The 2+2 state in 132Te is identified as the one-phonon mixed-symmetry state in a projectile Coulomb excitation experiment presenting a firm example of a mixed-symmetry state in unstable, neutron-rich nuclei. The results of shell-model calculations based on the low-momentum interaction VlOW_k are in good agreement with experiment demonstrating the ability of the effective shell-model interaction to produce states of mixed-symmetry character. [ABSTRACT FROM AUTHOR]