Coulomb shifts and shape changes in the mass 70 region

TL;DR

This paper introduces a recoil beta tagging technique to study excited states in nuclei far from stability, revealing anomalous Coulomb energy differences in the A=70 mass region likely due to shape changes.

Contribution

The paper develops a new recoil beta tagging method enabling observation of excited states and Coulomb energy differences in exotic nuclei, providing insights into nuclear shape effects.

Findings

First observation of excited states in 78Y

Extended knowledge of T=1 states in 74Rb

Anomalous Coulomb energy difference behavior in A=70 nuclei

Abstract

The technique of recoil beta tagging has been developed which allows prompt gamma decays in nuclei from excited states to be correlated with electrons from their subsequent short-lived beta decay. This technique is ideal for studying nuclei very far from stability and improves in sensitivity for very short-lived decays and for high decay Q-values. The method has allowed excited states in 78Y to be observed for the first time, as well as an extension in the knowledge of T=1 states in 74Rb. From this new information it has been possible to compare Coulomb energy differences (CED) between T=1 states in 70Br/70Se, 74Rb/74Kr, and 78Y/78Sr. The A=70 CED exhibit an anomalous behavior which is inconsistent with all other known CED. This behavior may be accounted for qualitatively in terms of small variations in the Coulomb energy arising from shape changes.