The structure of Ra-229 has been studied in the β- decay of Fr-229. Spins and parities have been determined from the conversion electron measurements, while half-lives for the 137.5, 142.7, 168.8, 213.0 and 479.0 keV levels have been measured in the ps and ns ranges via the fast timing βγγ(t) method. Our data confirm the previous results and enrich the knowledge of the structure of this nucleus by 25 new states and several strong transitions. Structural similarities are established between Ra-229 and its N = 141 isotone Th-231. The experimental results are compared with the theoretical predictions of the quasiparticle-phonon model with inclusion of Coriolis coupling. The reduced transition probabilities, and especially the moderately fast B(E1) rate for the 137.5 keV transition connecting the band-heads of the K-π = 5/2(±) parity doublet bands, reveal the presence of significant octupole correlations in Ra-229.

This work was partially supported by the Spanish CICYT "Plan National de Altas Energias" (under contracts AEN96-1662 and AEN96-1679), the Margit & Folke Pehrzon Foundation, the Swedish Natural Science Research Council, Czech Republic Grant Agency (under contract 202/96/ 1744) and the Polish Scientific Research Committee (under grant KBN-2-P03B-OOl-11).

36 pages, 5 tables, 9 figures.-- PACS nrs.: 23.20.−g; 21.10.Tg; 21.10.Re; 27.90.+b.

Peer reviewed