Structure of high-lying levels populated in the ⁹⁶Y → ⁹⁶Zr β decay

The nature of Jπ=1− levels of 96Zr below the β-decay Qβ value of 96Y has been investigated in high-resolution γ-ray spectroscopy following the β decay as well as in a campaign of inelastic photon scattering experiments. Branching ratios extracted from β decay allow the absolute E1 excitation strength to be determined for levels populated in both reactions. The combined data represents a comprehensive approach to the wavefunction of 1− levels below the Qβ value, which are investigated in the theoretical approach of the Quasiparticle Phonon Model. This study clarifies the nuclear structure properties associated with the enhanced population of high-lying levels in the 96Ygs β decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum