Total Absorption Spectroscopy of Neutron Rich Nuclei Across the N=50 Neutron Shell Closure

Decay spectroscopy of neutron rich nuclei near doubly magic 78^Ni [78-Nickel] is relevant to nuclear structure and astrophysics as well as reactor and neutrino physics. β-decay [beta-decay] calorimetry studies are essential to reconstruct the decay strength function and is used to overcome the problems arising from the high density of states leading to nuclear Pandemonium. The Modular Total Absorption Spectrometer, currently located in HRIBF at the Oak Ridge National Laboratory, collected data on 25 fission products of ²³⁸U [238-Uranium] during a run in March 2015. Analysis of the ^84,85,86Br [84, 85 and 86-Bromine] data from the March 2015 run indicates a significant modification of the β-strength [beta-strength] function when compared with previous measurements for all three nuclei, including the introduction of new high energy states not previously detected. The cases of ^84,85,86Br will be discussed in concert with shell model predictions. ⁸⁵Br [85-Bromine] is a singly magic N=50 nucleus. Through the study of N=49,50,51 nuclei the decay properties around a neutron shell closure governed by the interplay between core and valence nucleon excitations and Gamow-Teller decay in a ⁷⁸Ni [78-Nickel] core can be understood and provide a pinpoint for the study of more exotic nuclei.