Multiple-bands structures in the 223-Th-133 nucleus. Quadrupole-Octupole collectivity in the A∼220 mass region of the nuclear map

Abstract

Excited states in the 223-Th nucleus have been studied. The nucleus presents one of the best examples for parity-doublet structures. The nucleus has been revisited in an experiment using the 80 MeV 18-O+208-Pb→223-Th+3n reaction, the GAMMASPHERE γ-ray and the HERCULES evaporation-residue detector arrays. This work presents a description on the experiment, a status report on the analysis and a discussion of the results. The study of the 223-Th involved the delineation of the high-spin behavior of the yrast structure, i.e. parity splitting as a function of spin where three strict parity doublets have been identified, and also, a tentative fourth parity level on the new structures. A pursuit for a K 5/2 structure was made by the analysis of the parity splitting. The level scheme for 223-Th was constructed with 26 new γ-ray transitions and 17 new energy levels, but there is not evidence of non-yrast structures due the lack of E2-type transitions. New transitions were found for the 220-Ra and 224-Th, one for each one.