Nuclear structure of Th229

Lifetimes of excited states in Th229, populated in the β decay of Ac229, have been measured using the advanced time-delayed βγγ(t) method. Half-lives of 14 states have been determined including 11 of them for the first time. Twenty-seven new γ lines have been introduced into the β-decay scheme of Ac229 based on results of γγ coincidence measurements. Reduced transition probabilities have been determined for more than 70 γ transitions in Th229. Average |D₀| values of 0.029(1), 0.077(3), and 0.024(5) e fm have been deduced for the lowest K^π=1/2^±,3/2^±, and 5/2^± parity partner bands, respectively. Excited states in Th229 and experimental transition rates have been interpreted within the quasiparticle-plus-phonon model. The half-life of the 3.5-eV, 3/2⁺ isomeric state is predicted to be about 10 h. Potential energy surfaces on the (β₂,β₃) plane for the lowest single quasiparticle configurations in Th229 have been calculated using the Strutinsky method.