首次建立缺中子核素~(209)Fr的分支比很弱的(EC+β~+)衰变纲图

Abstract

用１６Ｏ束轰击１９７Ａｕ靶，通过熔合蒸发４ｎ反应产生了２０９Ｆｒ，借助于氦喷嘴带传输系统对其衰变性质进行了研究．由－ｔ，Ｘ－－ｔ，－－ｔ符合及－延迟符合测量得到的结果，首次建立了２０９Ｆｒ的（ＥＣ＋β＋）衰变纲图．它包含了２０条射线．２０９Ｒｎ的５个低位态的成员可以用［（２１０Ｒｎ２＋）（νｆ５／２）－１］多重态结构来解释．实验估计２０９Ｆｒ（ＥＣ＋β＋）衰变的分支比为（３．０±１．５）％．Fr has been produced by irradiation of 197 Au with 16 O from SFC accelarator uia the fusion evaporation 4n channel.The (EC+β +)decay of 209 Fr has been studied by a He jet tape transport system.The decay scheme is proposed for the first time based on -t,X--t,--t coincidece and - delay coincidence measurements,which takes account of 20 observed  ray.Five members of low lying states in 209 Rn can be explained by the multiplet [( 210 Rn 2 +)(νf 5/2 ) -...中国科学院和国家自然科学基