The nuclear structure of $^{229}$Th

The $\gamma$-rays following the $\beta\!^{-}$-decay of $^{229}$Ac have been investigated by means of $\gamma$-ray singles and $\gamma\gamma$-coincidence measurements using Ge detectors. Multipolarities of 40 transitions in $^{229}$Th have been established by measuring conversion electrons with a mini-orange electron spectrometer. The half-lives of the 146.35, 164.53 and 261.96 keV levels have been measured using the advanced time-delayed $\beta\gamma\gamma$(t)- method. The low-lying states in $^{229}$Th and observed transition rates have been interpreted within the quasiparticle-phonon model with inclusion of Coriolis coupling. Two octupole correlated parity partner bands, with K$^{\pi}=5/2^{\pm}$ and K$^{\pi}=3/2^{\pm}$, were identified in $^{229}$Th.