【摘要】 利用 10 2MeV16O6+束轰击同位素靶117Sn ,通过熔合蒸发 4n反应产生核素12 9Ce.由氦喷嘴快速带传输系统将反应产物送到低本底区 .通过化学分离来制备待测的Ce样品 ,与此同时用16O束轰击117Sn的两种相邻的同位素靶118Sn和116Sn ,并比较上述 3种反应中的产物来进一步区分元素Ce的不同的同位素 .结果一种半衰期为 4.1min的活性被鉴定为12 9Ce.基于X -γ -t和γ -γ -t符合测量 ,建议了包括 5 1条射线在内的12 9Ce的 (EC/ β+)衰变纲图 .其中 ,12 9Ce基态直接馈送到12 9La基态的份额 ( 2 6± 7) %是用观测到的12 9La衰变的 2 78.6keV的γ射线的生长和衰变曲线估计出来的 .另外还给出了用La Kα X射线和6 8.2keVγ射线开门的γ谱以及典型的衰变γ射线的时间谱更多还原

【Abstract】 The nuclide 129 Ce was produced by a ( 16 O,4n) reaction with an enriched 117 Sn 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 117 Sn, 116 Sn and 118 Sn,were also bombarded with 16 O 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 129 Ce. Based on X γ t and γ γ t coincidence measurements, the EC/β + decay scheme of 129 Ce, including 51 γ lines,was proposed. Using the observed growth decay curve of an intense 278.6keV γ line of 129 La decay, the β feeding branch from the ground state of 129 Ce directly to the ground state of 129 La was estimated to be (26±7)%. In addition, the γ spectra gated by both La K α X ray and intense 68.2keV γ ray of 129 Ce decay as well as the time spectra of typical γ rays were also presented here.更多还原