The nuclear structure of Th-229

Abstract

The γ-rays following the β- decay of Ac-229 have been investigated by means of γ-ray singles and γγ-coincidence measurements using Ge detectors. Multipolarities of 40 transitions in Th-229 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 betagammagamma(t) method. The low-lying states in Th-229 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-π = 5/2(±) and K-π = 3/2(±), were identified in Th-229.