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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
The isotope target 117Sn was bombarded with a 10 2 MeV 16 O 6 + beam and the nuclide 12 9Ce was generated by the fusion-evaporation 4n reaction. The reaction product was sent to the low background zone by a helium nozzle rapid tape delivery system. The Ce sample to be measured was prepared by chemical separation, At the same time, two adjacent isotope targets 118Sn and 116Sn of 117Sn were bombarded with 16O beams and the products of the above three reactions were compared to further discriminate the different isotopes of the elemental Ce.Results A half-life of 4.1min was identified as 12 Based on the coincidence measurements of X-γ-t and γ-γ-t, we propose a (EC / β +) decay scheme of 12 9 Ce with 5 1 rays, in which the 12 9Ce ground state is directly fed to 12 9La The ground state contribution (26 ± 7)% was estimated from the observed growth and decay curves for 2 78.6 keV gamma decay at 12 9 La. In addition, the La Ka X-ray and 6 8.2 keV gamma rays were used to open the door Γ spectrum and the typical decay γ-ray time spectrum