Shape transitions between and within Zr isotopes

The Zirconium isotopes across the N=56,58 neutron sub-shell closures have been of special interest since years, sparked by the near doubly-magic features of Zr-96 and the subsequent rapid onset of collectivity with a deformed ground-state structure already in Zr-100. Recent state-of-the-art shell model approaches did not only correctly describe this shape-phase transition in the Zr isotopic chain, but also the coexistence of non-collective structures and pronounced collectivity especially in Zr-96,Zr-98. The isotope Zr-98 is located on the transition from spherical to deformed ground state structures. We summarize recent experimental work to obtain the B(E2) excitation strengths of the first 2(+) state of Zr-98, including a new experiment employing the recoil-distance Doppler-shift method following a two-neutron transfer reaction.