Nuclear structure ofTh229

Abstract

Lifetimes of excited states in {sup 229}Th, populated in the {beta} decay of {sup 229}Ac, have been measured using the advanced time-delayed {beta}{gamma}{gamma}(t) method. Half-lives of 14 states have been determined including 11 of them for the first time. Twenty-seven new {gamma} lines have been introduced into the {beta}-decay scheme of {sup 229}Ac based on results of {gamma}{gamma} coincidence measurements. Reduced transition probabilities have been determined for more than 70 {gamma} transitions in {sup 229}Th. Average |D{sub 0}| values of 0.029(1), 0.077(3), and 0.024(5) e fm have been deduced for the lowest K{sup {pi}}=1/2{sup {+-}},3/2{sup {+-}}, and 5/2{sup {+-}} parity partner bands, respectively. Excited states in {sup 229}Th and experimental transition rates have been interpreted within the quasiparticle-plus-phonon model. The half-life of the 3.5-eV, 3/2{sup +} isomeric state is predicted to be about 10 h. Potential energy surfaces on the ({beta}{sub 2},{beta}{sub 3}) plane for the lowest single quasiparticle configurations in {sup 229}Th have been calculated using the Strutinsky method.