Total Absorption Gamma-Ray Spectroscopy of 87Br, 88Br and 94Rb Beta-Delayed Neutron Emitters

Abstract

We investigate the decay of 87Br, 88Br and 94Rb using total absorption gamma-ray spectroscopy. These important fission products are beta-delayed neutron emitters. Our data show considerable gamma-intensity, so far unobserved in high-resolution gamma-ray spectroscopy, from states at high excitation energy. We also find significant differences with the beta intensity that can be deduced from existing measurements of the beta spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the range 1 to 100 s. We also use summation calculations to evaluate the impact of present data on reactor antineutrino spectra. We find a significant effect at antineutrino energies in the range of 5 to 9 MeV. In addition, we observe an unexpected strong probability for gamma emission from neutron unbound states populated in the daughter nucleus. The gamma branching is compared to Hauser-Feshbach calculations which allow one to explain the large value for bromine isotopes as due to nuclear structure. However the branching for 94Rb, although much smaller, hints of the need to increase the radiative width by one order-of-magnitude. This leads to a similar increase in the calculated (n,gamma) cross section for this very neutron-rich nucleus with a potential impact on r-process abundance calculations.

References in corpus (4)

• The Reactor Antineutrino Anomaly
• Improved measurements of the neutrino mixing angle ${\theta }_{13}$ with the Double Chooz detector
• Dynamical r-process studies within the neutrino-driven wind scenario and its sensitivity to the nuclear physics input
• Spectral Structure of Electron Antineutrinos from Nuclear Reactors

Cited by in corpus (13)

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• Reactor antineutrino flux and anomaly
• PROSPECT-II Physics Opportunities
• ${\beta }^{-}$ decay study of the ${}^{66}$Mn - ${}^{66}$Fe - ${}^{66}$Co - ${}^{66}$Ni chain
• First $\beta$-decay spectroscopy of ${}^{135}$In and new $\beta$-decay branches of ${}^{134}$In
• First measurements with a new $\beta$-electron detector for spectral shape studies
• Model-Independent Determination of Isotopic Cross Sections per Fission for Reactor Antineutrinos
• Simultaneous impacts of nuclear shell structure and collectivity on $\beta$ decay: Evidence from ${}^{80}$Ga${}_{49}$
• Study of beta spectrum shapes relevant to the prediction of reactor antineutrino spectra
• Correcting for neutron width fluctuations in Hauser-Feshbach gamma branching ratios