β decay of Ba141

Abstract

The $\ensuremath{\beta}$-decay strength function of nuclides produced in fission is important as it dictates the distribution of decay energy between electrons, neutrinos, and $\ensuremath{\gamma}$ rays and so is critical for calculating decay heat in reactors and for estimating the reactor antineutrino spectrum. Several experimental techniques are available to determine this strength function, including electron spectroscopy, $\ensuremath{\gamma}$-ray calorimetry (TAGS spectroscopy), and detailed, high-resolution spectroscopy with modern large high-purity germanium arrays. This work investigates the decay of the well-known and strongly produced fission fragment $^{141}\mathrm{Ba}$. A beam of $^{141}\mathrm{Cs}$ was implanted at the target position of the Gammasphere and the subsequent decay of the daughter $^{141}\mathrm{Ba}$ was studied. Extensive decay spectroscopy was possible up to the decay $Q$ value of 3.197(7) MeV, including a significant extension of the level scheme and detailed angular correlation measurements for all levels with greater than $0.25%\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$ feeding. The distribution of the $\ensuremath{\beta}$-decay strength was then inferred and compared to previous calorimetric studies. The agreement was excellent and provides a benchmark for comparing strength function methods and data for a more detailed understanding of the structure of $^{141}\mathrm{La}$.