Nuclear structure of 229Th from γ-ray spectroscopy study of 233U α-particle decay -: art. no. 034329

The level structure of Th-229, produced by alpha-particle decay of U-233, was studied with gamma-ray spectroscopy measurements. The sources were continuously separated from daughters with ion-exchange chromatographic methods. Singles and coincidence measurements were performed with high-purity germanium detectors. Energies and intensities of about 220 gamma rays were accurately determined. About 70 transitions were reported for the first time, especially in the 300-700 keV energy range. A Th-229 level scheme was proposed, accounting for 220 transitions among 47 excited states. Alpha-particle feeding intensities and hindrance factors were deduced and compared to direct alpha-particle measurements; the agreement was found to be relatively good. The level structure was interpreted in the framework of rotational and/or reflection asymmetric models. The agreement with experimental data was shown to be satisfactory.