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The reduced transition probabilities B ( E 2 ; 0 g.s. + → 2 1 + , 2 2 + ) in Zn 70 and the full B ( E 2 ; 0 g.s. + → 2 + ) strength up to S n = 7.79 MeV in Ni 68 have been determined at the LISE/GANIL facility using the Coulomb-excitation technique at intermediate beam energy on a Pb 208 target. The γ rays emitted in-flight were detected with an array of 46 BaF 2 crystals. The angles of the deflected nuclei were determined in order to disentangle and extract the Coulomb and nuclear contributions to the excitation of the 2 + states. The measured B ( E 2 ; 0 g.s. + → 2 1 + ) of 1432(124) e 2 fm 4 for Zn 70 falls in the lower part of the published values which clustered either around 1600 or above 2000 e 2 fm 4 , while the B ( E 2 ; 0 g.s. + → 2 2 + ) of 53(7) e 2 fm 4 agrees very well with the two published values. The relatively low B ( E 2 ; 0 g.s. + → 2 1 + ) of 301(38) e 2 fm 4 for Ni 68 agrees with previous studies and confirms a local magicity at Z = 28 , N = 40 . Combining the results of the low-energy spectra of Ni 68 and Zn 70 and their shell-model interpretations, it is interesting to notice that four different shapes (spherical, oblate, prolate, and triaxial) are present. Finally, a summed E 2 strength of only about 150 e 2 fm 4 has been found experimentally at high excitation energy, likely due to proton excitations across the Z = 28 gap. The experimental distribution of this high-energy E 2 excitation agrees with shell-model calculations, but its strength is about two times weaker.

International audience; The overlap in the mass symmetric region of the reaction products from fusion-fission and quasifission complicates the assignment of symmetric events to complete fusion on the basis of the mass distribution alone. Additional observables, besides mass distribution, should be used. The approach proposed here relies on the fact that fusion-fission and quasifission are characterized by different timescales. Within this framework, we performed a detailed study to find out how timescales can be probed via angular momentum transfer as measured via γ-ray multiplicities. The proof of principle was carried out by measuring the γ rays in coincidence with fusion-fission and quasielastic binary fragments in the reaction S32 + Au197 at beam energy near the Coulomb barrier. The experiment was performed at the Accélérateur Linéaire Tandem à Orsay (ALTO) facility at the Institut De Physique Nucléaire (IPN) in Orsay (France) using a detection setup consisting of ORGAM (ORsay GAMma) and PARIS (Photon Array Radioactive Ion Stable beams) γ-detectors arrays coupled with the CORSET (CORrelation SETup) time-of-flight spectrometer. Results of the sensitivity of this method to distinguish reaction channels with different dynamics are discussed.

The structure of $^{34}$Si was studied through $\gamma$ spectroscopy separately in the $\beta^-$ decays of $^{34}$Mg and $^{34}$Al at the ISOLDE facility of CERN. Different configurations in $^{34}$Si were populated independently from the two recently identified $\beta$-decaying states in $^{34}$Al having spin-parity assignments $J^\pi = 4^-$ dominated by the normal configuration $\pi (d_{5/2})^{-1} \otimes \nu (f_{7/2})$ and $J^\pi = 1^+$ by the intruder configuration $\pi (d_{5/2})^{-1} \otimes \nu (d_{3/2})^{-1}(f_{7/2})^{2}$. The paper reports on spectroscopic properties of $^{34}$Si such as an extended level scheme, spin and parity assignments based on log($ft$) values and $\gamma$-ray branching ratios, absolute $\beta$ feeding intensities and neutron emission probabilities. A total of 11 newly identified levels and 26 transitions were added to the previously known level scheme of $^{34}$Si. Large scale shell-model calculations using the {\sc sdpf-u-mix} interaction, able to treat higher order intruder configurations, are compared with the new results and conclusions are drawn concerning the predictive power of {\sc sdpf-u-mix}, the $N=20$ shell gap, the level of mixing between normal and intruder configurations for the 0$_1^+$, 0$_2^+$ and 2$_1^+$ states and the absence of triaxial deformation in $^{34}$Si.

The decays of two isomeric states in the neutron-rich nucleus $^{75}\mathrm{Cu}$ have been studied via delayed $\ensuremath{\gamma}$-ray spectroscopy. These states were populated by the fragmentation of a $60.4\phantom{\rule{4pt}{0ex}}A\phantom{\rule{0.16em}{0ex}}\mathrm{MeV} ^{86}\mathrm{Kr}$ primary beam, which impinged on a Be target at the LISE2k spectrometer of GANIL. Isomeric half-lives and branching ratios were measured, and a $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence analysis performed. These have allowed a revised level scheme of $^{75}\mathrm{Cu}$ to be proposed. A comparison with large-scale shell-model calculations using different effective interactions and valence spaces shows the importance of proton excitations across the $Z=28$ shell gap for reproducing the energy spacing between the isomeric states. The coexisting collective and single-particle properties of the $(1/{2}^{\ensuremath{-}})$ and $(3/{2}^{\ensuremath{-}})$ states, respectively, are similar to those of the same states in the neighboring $^{69,71,73}\mathrm{Cu}$. The small energy spacings between the $(1/{2}^{\ensuremath{-}}), (3/{2}^{\ensuremath{-}})$, and $5/{2}^{\ensuremath{-}}$ states are responsible for the isomerism.

The reduced transition probabilities B(E2; 0+ g.s. → 2+ 1 ) of the 46Ar and 44Ca nuclei were studied using the Coulomb excitation technique at intermediate energy at the LISE/GANIL facility. The in-flight γ rays, emitted after the Coulomb excitation of their first 2+ states, were detected in an array of 64 BaF2 crystals. The present B(E2 ↑) value for 44Ca, 475(36) e2fm4 , agrees well with the value of 495(35) e2fm4 obtained by averaging results of previous experiments. Consistent B(E2; 0+ g.s. → 2+ 1 ) values of 225(29) e2fm4 and 234(19) e2fm4 have been obtained for 46Ar from an absolute and a relative measurement, normalized to the 44Ca value. Both results agree with the ones obtained with the same experimental technique at the NSCL facility but are a factor of 2 smaller than the shell model predictions. The drop in B(E2; 0+ g.s. → 2+ 1 ) in the Ar chain at N = 28, confirmed in this experiment, shows that 46Ar is sensitive to the N = 28 shell closure.