The alpha decay study of223Th (T 1/2=0.6 s)

The219Ra levels, fed by the α-decay of223Th, have been studied by anα−γ coincidence experiment. AK=1/2+ band, based on the 7/2+ ground state, with a large decoupling parameter a=−5.5 is proposed. Three levels with spins 5/2, 9/2, 7/2 and lowα-hindrance factors around 140 keV, can be considered as members of aK=5/2+ band, perturbed by the Coriolis coupling of configurations arising from theg9/2 shell. TheseK =1/2+ and 5/2+ orbitals are expected forN=131 in the reflection asymmetry model with ɛ2≃ɛ3−0.1. How-ever no evidence was found for the corresponding negative parity bands in this transitional nucleus.