Jacob Heery

Lead-208 is the heaviest known doubly magic nucleus and its structure is therefore of special interest. Despite this magicity, which acts to provide a strong restorative force toward sphericity, it is known to exhibit both strong octupole correlations and some of the strongest quadrupole collectivity observed in doubly magic systems. In this Letter, we employ state-of-the-art experimental equipment to conclusively demonstrate, through four Coulomb-excitation measurements, the presence of a large, negative, spectroscopic quadrupole moment for both the vibrational octupole 3 1 − and quadrupole 2 1 + state, indicative of a preference for prolate deformation of the states. The observed quadrupole moment is discussed in the context of the expected splitting of the 3 − ⊗ 3 − two-phonon states, due to the coupling of the quadrupole and octupole motion. These results are compared with theoretical values from three different methods, which are unable to reproduce both the sign and magnitude of this deformation. Thus, in spite of its well-studied nature, Pb 208 remains a puzzle for our understanding of nuclear structure.

The neutron -rich strontium, zirconium, and molybdenum nuclei have been observed to undergo a dramatic evolution, becoming strongly deformed around N = 60, sometimes interpreted as a quantum phase transition between "normal" and intruder configurations. Key to understanding this evolution is to understand the configurations in isolation, in regions where interference can be neglected. A deformed coexisting configuration is inferred from the presence of a 0 2 state which decreases in excitation energy with increasing neutron number, becoming the first -excited state at 98Mo. We present here the results of a low -energy Coulomb -excitation measurement of the nucleus 96Mo, extracting B(E2) values and quadrupole moments. It is found that, while the B(E2) values agree with those found in the literature, there is a significant disagreement with literature spectroscopic quadrupole moments. The results are compared with shell -model calculations using a 88Sr core with good agreement found, likely indicating that intruder structures do not significantly impact the ground -state structure, in contrast with the heavier molybdenum isotopes.

Lifetime measurements in Pt-178 with excited states de-exciting through gamma-ray transitions and internal electron conversions have been performed. Ionic charges were selected by the in-flight mass separatorMARAand measured at the focal plane in coincidence with the 4(1)(+) -> 2(1)(+) 257 keV gamma-ray transition detected using the JUROGAM 3 spectrometer. The resulting charge-state distributions were analysed using the differential decay curve method (DDCM) framework to obtain a lifetime value of 430(20) ps for the 2(1)(+) state. This work builds on a method that combines the charge plunger technique with the DDCM analysis. As an alternative analysis, ions were selected in coincidence with the Pt-178 alpha decay (E-alpha = 5.458(5) MeV) at the focal plane. Lifetime informationwas obtained by fitting a two-state Bateman equation to the decay curve with the lifetime of individual states defined by a single quadrupolemoment. This yielded a lifetime value of 430(50) ps for the 2(1)(+) state, and 54(6) ps for the 4(1)(+) state. An analysis method based around the Bateman equation will become especially important when using the charge plunger method for the cases where utilising coincidences between prompt gamma rays and recoils is not feasible.