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

The nature of the high-lying final levels of the 96Ygs beta decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum, has been investigated in high-resolution gamma-ray spectroscopy following the beta decay as well as in a campaign of inelastic photon scattering experiments. The comprehensive approach establishes 1- levels associated with the Pygmy Dipole Resonance as high-lying final levels in the beta decay. Branching ratios extracted from beta decay complement photon scattering and 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 the 1- levels below the Q beta value, which are investigated in the Quasiparticle Phonon Model. The calculations reveal that the components populated in beta decay contribute only with small amplitudes to the complex wavefunction of these 1- levels. A comparison of the beta decay results to data from total absorption gamma-ray spectroscopy demonstrates a good agreement between both measurements. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.

Automated summary

The nature of the high-lying final levels of 96Ygs beta decay has been investigated using high-resolution gamma-ray spectroscopy and inelastic photon scattering experiments, revealing 1- levels associated with the Pygmy Dipole Resonance. A comprehensive approach was used to determine the wavefunction and absolute E1 excitation strength, with comparisons between beta decay and total absorption gamma-ray spectroscopy showing good agreement.