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The decay of radiochemically-separated Ac sources has been reinvestigated using highresolution coaxial HPGe detectors and y-y coincidence measurements. Energies and intensities of more than 240 photons were accurately measured, 80 of them for the first time. A ' 'Th level scheme, built on the bases of good energy fits and on y-y coincidence data, involves 58 excited states, of which 17 are new, up to 2159 keV with spin 0(I (6. Collective properties of lowenergy states belonging to K =0,2+,2 bands are discussed in the framework of the Bohr-Mottelson model. Decay modes of a K =0+ excited band at 831.82 keV favor strong two octupole phonon K =0 components. The K"=1 band is expected to have I =2 and 3 members at 938.5 and 968.4 keV. Coriolis coupling calculations involving the four K =0, 1, 2, and 3 bands were carried out. Tentative K =2+ two-quasiparticle bands at 1638.23 and 1899.99 keV are discussed in terms of Nilsson orbitals.

The ' C decay of Ra has been reinvestigated, using an 85 MBq activity ' U source radiochemically separated, a Si barrier detector, and a superconducting magnetic spectrometer. In a 16 days counting run, 210 ' C events were recorded. The ' C particles energy value 30.930+0.090 MeV was found and an upper limit b~2X10 ' was estimated for the ' C branching ratio to the 'Pb first excited state; the branching-ratio value to the 'Pb ground state, thus equal to the total branching ratio, was found to be b =A, , /A. =(2.31+0.31)X 10

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A radiochemical separation is presented for americium, plutonium and neptunium from sediment samples by using an unique anionic exchange process. An oxidation-reduction step was introduced in the classical procedure of the radiochemical determination of transuranic elements in order to control the valence of the separated elements.

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