Search

International audience; The lifetimes of the $ 2^+_1$ , the $ 2^+_2$ and the $ 3^-_1$ states of$^{210}$Po have been measured in the$^{208}$Pb($^{12}$C,$^{10}$Be)$^{210}$Po transfer reaction by the Doppler-shift attenuation method. The result for the lifetime of the $ 2^+_1$ state is about three times shorter than the adopted value. However, the new value still does not allow for a consistent description of the properties of the yrast $ 2^+_1$ , $ 4^+_1$ , $ 6^+_1$ , and $ 8^+_1$ states of$^{210}$Po in the framework of nuclear shell models. Quasi-particle Phonon Model (QPM) calculations also cannot overcome this problem thus indicating the existence of a peculiarity which is neglected in both theoretical approaches.

WOS: 000257770700017 The even-even Selenium isotopes in the A similar to 80 mass region and the general features of its structure have been investigated within the framework of the interacting boson model-2. The neutron proton version of the model has been applied to the Se (A=74 to 80) isotopes with emphasis on the description of the 0(1)(+), 2(1)(+), 0(2)(+), 2(2)(+), and 4(1)(+) states. The energy levels, B(E2)and B(M1)electromagnetic transition probabilities were calculated. The results of these calculations were compared with previous experimental results and were shown to be in good agreement.

International audience; The t(6He,8He)p t(8He,10He)p reactions were studied in experiments with 25A MeV 6He beam and 27.4A MeV 8He beams and an unique tritium gas target. Results on the 8He and 10He excitation energy spectra are presented. The 8He spectrum exhibits 3 states, apart of the ground state and known (2+) state at 3.6 MeV, the third state is seen at 5.4 MeV. A tentative assignment 1+ is proposed for this structure. The 10He spectrum shows no event at the excitation energy below 3 MeV what is in contradiction with the earlier reports on this nucleus. A high statistics of α-n coincidence events collected for the 8He beam run has been subjected to analysis in order search for the bound tetraneutron. The search produced a negative result.

The experimental charge radius values along Cd, Sn, Te, Xe, Ba and Sm isotopic series have been extracted from isotope shift measurements using different methods to calibrate the electronic factor and mass shift effects. Static and dynamic charge radii have been calculated in the framework of a microscopic configuration mixing approach on the ground of Hartree–Fock–Bogoliubov solutions obtained with the D1S Gogny effective nucleon–nucleon interaction. Low-energy spectroscopic observables have also been obtained. The theoretical and experimental results are compared and discussed. It is shown that dynamical effects must be taken into account especially for γ -soft and weakly deformed nuclei.

Lifetimes of exited states in $^{134}$Pr were measured by means of the recoil distance Doppler-shift and Doppler-shift attenuation techniques. The branching ratios and the electric or magnetic character of the transitions were also investigated. The experiments were performed at IReS, Strasbourg, using the EUROBALL IV spectrometer, in conjunction with the inner bismuth germanate ball and the Cologne coincidence plunger apparatus. Exited states in $^{134}$Pr were populated in the fusion-evaporation reaction $^{119}Sn(^{19}F, 4n)^{134}$Pr. The possible chiral interpretation of twin bands was investigated in the two-quasiparticle triaxial rotor and interacting boson-fermion-fermion models. The analysis of the wave functions has shown that the possibility for the angular momenta of the proton, neutron, and core to find themselves in the favorable, almost orthogonal geometry, is present but is far from being dominant. The structure is characterized by large $\beta$ and $\gamma$ fluctuations. The existence of doublets of bands in $^{134}$Pr can be attributed to weak chirality dominated by shape fluctuations.

NESTER; Differential cross section of the inelastic scattering of a 54 MeV/u 26Ne beam on a lead target has been measured by detecting the de-excitation $\gamma$-rays. Analysis of the first 2+ state angular distribution of the inelastically scattered nuclei shows that the process cannot be considered as a pure Coulomb excitation, and nuclear contribution must be taken into account. The charge deformation deduced, ¯C 2 = 0.392 ± 0.024, corresponds to a B(E2) = 141 ± 18 e2fm4 in agreement with a N = 16 sub-shell closure.

International audience; This paper presents a search for the competing 11/2 − → 1/2 + E5 branch to the main 11/2 − → 3/2 + M4 transition from the T 1/2 = 39 h, J π = 11/2 − isomeric state in 133 Ba. An upper limit of 1.8 * 10 −5 could be established for the E5/M4 intensity ratio. In addition a long-standing controversy in the EC-decay of the same isomer was resolved: only one EC branch to the 11/2 + state in 133 Cs was observed. The shell-model structures of the involved states in 133 Ba and 133 Cs were studied with the microscopic quasiparticle-phonon model (MQPM). Good agreement with the decay rates B(λ) was obtained. In particular, the B(M4) value is well reproduced and further only one low-lying 11/2 state could be identified in the latter nuclide, supporting the experimental results.