(EC+beta(+)) decay of neutron-deficient nuclide Ce-129

The nuclide Ce-129 was produced by a (O-16,4n) reaction with an enriched Sn-117 target. With the aid of a helium-jet tape transport system, the reaction products were transported to a shielded location,where Ce samples were prepared after chemical separation. The neighboring isotopes of Sn-117, Sn-116 and Sn-118,were also bombarded with O-16 beam. Different isotopes of Ce were further separated by comparing the products in the above three reactions. An activity with a half-life of 4.1 min in the chemically purified cerium samples was identified as Ce-129. Based on X-gamma -t and gamma-gamma -t coincidence measurements, the EC/beta (+) decay scheme of Ce-129, including 51 gamma lines, was proposed. Using the observed growth-decay curve of an intense 278.6keV gamma line of La-129 decay, the beta feeding branch from the ground state of Ce-129 directly to the ground state of La-129 was estimated to be (26 +/- 7) %. In addition, the gamma spectra gated by both La-K-alpha-X ray and intense 68.2keV gamma ray of Ce-129 decay as well as the time spectra of typical gamma rays were also presented here.