Search

The half-lives of $2^+_1$ states were measured for $^{102,104}$Zr and $^{106,108}$Mo to test a new implementation of a LaBr$_3$(Ce) array at the RIBF, RIKEN, Japan. The nuclei of interest were produced through the fission of a 345~MeV/nucleon $^{238}$U beam and selected by the BigRIPS separator. Fission fragments were implanted into the WAS3ABi active stopper, surrounding which, 18 LaBr$_3$(Ce) detectors provided fast $\gamma$-ray detection. Timing between the LaBr$_3$(Ce) array and plastic scintillators allowed for the measurement of half-lives of low-lying states. The preliminary results, which agree with literature values, are presented along with experimental details.

It has been shown that the neutron 2d5=2 orbital has to be included in shell-model calculations to explain the large quadrupole collectivity observed in the Fe and Cr of N = 40 region, probably a new island of inversion similar to the one known for light nuclei around N = 20. Indeed, in these calculations using a large valence neutron space, the position, i.e. the singleparticle energy, of the 2d5=2 orbital is a crucial ingredient. The experiment discussed in this paper aims to determine the $\nu$1g9=2–$\nu$2d5=2 gap using the neutron stripping reaction d(68Ni; p)68Ni which has been performed at GANIL in inverse kinematics. Preliminary results are presented.