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Rapid shape changes are observed for neutron-rich nuclei with A around 100. In particular, a sudden onset of ground-state deformation is observed in the Zr and Sr isotopic chains at N=60: low-lying states in N≤58 nuclei are nearly spherical, while those with N≥60 have a rotational character. Nuclear lifetimes as short as a few ps can be measured using fast-timing techniques with LaBr 3 (Ce)-scintillators, yielding a key ingredient in the systematic study of the shape evolution in this region. We used neutron-induced fission of 241 Pu and 235 U to study lifetimes of excited states in fission fragments in the A∼100 region with the EXILL-FATIMA array located at the PF1B cold neutron beam line at the Institut Laue-Langevin. In particular, we applied the generalized centroid difference method to deduce lifetimes of low-lying states for the nuclei 98 Zr (N=58), 100 Zr and 102 Zr (N≥60). The results are discussed in the context of the presumed phase transition in the Zr chain by comparing the experimental transition strengths with the theoretical calculations using the Interacting Boson Model and the Monte Carlo Shell Model.

Excited states in 133 Sn were investigated through the β decay of 133 In at the ISOLDE facility. The ISOLDE Resonance Ionization Laser Ion Source (RILIS) provided isomer-selective ionization for 133 In, allowing us to study separately, and in detail, the β-decay branch of 133 In J π = (9/2 +) ground state and its J π = (1/2 −) isomer.

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