Speaker
Description
Higher order collective degrees of freedom are well-established in the composition of excited quantum states of the atomic nucleus. Octupole collectivity, associated with pear-shaped nuclei, has been the subject of intense theoretical and experimental study. Regions of octupole deformation are found above all the major shell gaps --- the so-called octupole magic numbers --- $Z,N = 34, 56, 88, 134$. Effects attributed to octupole collectivity are particularly prominent in the light-actinide region, confirmed by numerous studies on even-even isotopes of the U, Th, Ra, Rn, isotopic chains. However, experimental information on odd-mass isotopes in this mass region are sorely lacking. The odd-mass candidates are of particular interest due to the enhancement of octupole effects arising from the interaction of the unpaired nucleon with the deformed core. These systems also play a central role in atomic electric dipole moment (EDM) searches, where the static octupole deformation and presence of low-lying parity doublets significantly enhance the nuclear Schiff moment. We request 7 days of beam time bombarding a 2 mg/cm$^2$ $^{232}$Th target with an 833 MeV $^{136}$Xe beam, with the objective of populating odd-mass radon and radium isotopes via multinucleon transfer reactions. A particular focus is placed on $^{223}$Rn which is expected to exhibit a higher degree of octupole collectivity compared to its neighbours. Measurements of experimental observables easily derived from energy level schemes $(\Delta i_x, ~|D_0/Q_0|)$ will provide immediate insight into the strength and type of octupole collectivity in these nuclei. The precise atomic mass and charge selectivity offered by PRISMA is expected to overcome previous experimental shortcomings in being unable to identify $\gamma$ rays belonging to the odd mass candidates.
