Nuclear levels in ²³³Th excited by neutron capture

The excited levels in ²³³Th have been studied using thermal and average resonance neutron capture in ²³²Th. 2 keV and 24 keV neutron capture has been investigated at the Brookhaven HFBR filtered beam facility. Conversion electrons and low energy γ-rays following thermal neutron capture have been measured at the ILL, Grenoble. From the combination of these data a level scheme of ²³³Th is proposed, which includes all low-spin states up to about 900 keV. Nine Nilsson configurations have been identified. Several rotational bands are explained as β, γ and octupole vibrational excitations. β-vibrational bands coupled to the [631 ↓] Nilsson states could be identified from the observation of transitions having strong E0 admixtures.