Total Absorption Spectroscopy Study of the Beta Decay of ${}^{86}$Br and ${}^{91}$Rb

Abstract

The beta decays of ${}^{86}$Br and ${}^{91}$Rb have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the IGISOL facility in Jyväskylä and further purified using the JYFLTRAP. ${}^{86}$Br and ${}^{91}$Rb are considered to be major contributors to the decay heat in reactors. In addition ${}^{91}$Rb was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam {\it et al.} assuming that this decay was well known from high-resolution measurements. Our results show that both decays were suffering from the {\it Pandemonium} effect and that the results of Rudstam {\it et al.} should be renormalized. The relative impact of the studied decays in the prediction of the decay heat and antineutrino spectrum from reactors has been evaluated.

11 pages, 13 figures