Advances in decay spectroscopy of 160Gd and developments for transfer experiments using radioactive isotope beams

[Abstract]

The structure of the atomic nucleus can rapidly evolve from a spherical shape into one with significant deformation as the number of protons and neutrons change within the nucleus. These exotic nuclei present the opportunity to study the evolution of the nuclear force via the resulting nuclear structure exhibited by the nucleus. In this work, the results of nuclear structure experiments on three isotopes are presented. These experiments, all performed at the TRIUMF-ISAC radioactive beam facility, help to improve understanding of the evolution of nuclear structure from single-particle to collective excitations in nuclei.

The structure of the highly-deformed 160Gd has been studied via the beta-decay of 160Eu using the GRIFFIN spectrometer. New measurements of spectroscopic information and lifetimes of excited-states has shed new light on the structure of K=4+ deformed bands located in this nucleus and supports these are being hexadecapole phonon bands. Lifetime measurements in 160Gd also show the 1999 keV state as having positive, not negative, parity. This result raises questions about the established structure of the beta-decaying states in the parent 160Eu.
Development and analysis in support of transfer reaction experiments at TRIUMF-ISAC was performed. Upgrades to the TRIFIC ionization chamber used in conjunction with the TIGRESS gamma-ray spectrometer are discussed. Experimental data from (d,p) neutron transfer reactions on the stable 86Kr and the radioactive 93Sr nucleus is presented here. In the resulting 87Kr, single-particle structure analysis of this data shows the evolution of neutron orbitals directly above the N=50 neutron shell closure. The structure of 94Sr was observed via (d,p) reactions on 93Sr. This experiment is the first ever population of 94Sr via a (d,p) reaction, and spectroscopic factors and angular distributions for a number of excited-states are first reported. The transfer data analysis on 86Kr and 93Sr is also in support of a larger experimental campaign using the Surrogate Reaction Method to experimentally constrain neutron capture cross-sections on unstable nuclei and briefly discussed here.