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The half-life of 19 Ne has been measured using a real-time digital multiparametric acquisition system providing an accurate time-stamp and relevant information on the detectors signals for each decay event. An exhaustive offline analysis of the data gave unique access to experimental effects potentially biasing the measurement. After establishing the influence factors impacting the measurement such as after-pulses, pile-up, gain and base line fluctuations, their effects were accurately estimated and the event selection optimized. The resulting half-life, 17.2569 ± 0.0019 (stat) ± 0.0009 (syst) s, is the most precise up to now for 19 Ne. It is found in agreement with two recent precise measurements and not consistent with the most recent one [L.J. Broussard et al., Phys. Rev. Lett. 112, 212301 (2014)] by 3.0 standard deviations. The full potential of the technique for nuclei with half-lives of a few seconds is discussed.

The gyromagnetic factor of the low-lying E = 251.96(9) keV isomeric state of the nucleus 99 Zr was measured using the Time Dependent Perturbed Angular Distribution technique. This level is assigned a spin and parity of J π = 7/2 + , with a half-life of T 1/2 = 336(5) ns. The isomer was produced and spin-aligned via the abrasion-fission of a 238 U primary beam at RIBF. A magnetic moment |µ| = 2.31( 14)µN was deduced showing that this isomer is not single-particle in nature. A comparison of the experimental values with Interacting Boson-Fermion Model IBFM-1 results shows that this state is strongly mixed with a main νd 5/2 composition. Furthermore it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.

Background: Classical novae result from thermonuclear explosions producing several γ-ray emitters which are prime targets for satellites observing in the MeV range. The early ≤ 511 keV gamma-ray emission depends critically on the 18 F(p,α) 15 O reaction rate which, despite many experimental and theoretical efforts, still remains uncertain.Purpose: One of the main uncertainties in the 18 F(p,α) 15 O reaction rate is the contribution in the Gamow window of interference between sub-threshold 19 Ne states and known broad states at higher energies. Therefore the goal of this work is to clarify the existence and the nature of these sub-threshold states.Method: States in the 19 Ne compound nucleus were studied at the Tandem-ALTO facility using the 19 F( 3 He,t) 19 Ne charge exchange reaction. Tritons were detected with an Enge Split-pole spectrometer while decaying protons or α-particles from unbound 19 Ne states were collected, in coincidence, with a double-sided silicon strip detector array. Angular correlations were extracted and constraints on the spin and parity of decaying states established. Results:The coincidence yield at Ex = 6.29 MeV was observed to be high spin, supporting the conclusion that it is indeed a doublet consisting of high spin and low spin components. Evidence for a broad, low spin state was observed around 6 MeV. Branching ratios were extracted for several states above the proton threshold and were found to be consistent with the literature. R-matrix calculations show the relative contribution of sub-threshold states to the astrophysically important energy region above the proton threshold. Conclusions:The levels schemes of 19 Ne and 19 F are still not sufficiently well known and further studies of the analogue assignments are needed. The tentative broad state at 6 MeV may only play a role if the reduced proton width is large.

International audienceThe fission of a variety of actinides was induced by fusion and transfer reactions between a 238U beam and 12C nuclei, in the active target MAYA. The performance of MAYA was studied, as well as its capability to reconstruct the fission-fragment trajectories. Furthermore, a full characterization of the different transfer reactions was achieved, and the populated excitation-energy distributions were investigated as a function of the kinetic energy in the entrance channel. The ratio between transfer-and fusion-induced fission cross-sections was also determined, in order to investigate the competition between both reaction types and its evolution with the incident energy. The experimental results will be discussed with a view to forthcoming radioactive-ion beam facilities, and next-generation active-target setups

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