首次测定短寿命缺中子同位素^（153）Er和^（157）Yb的EC／β~＋衰变  

First Study of EC/β￣+ Decay Schemes for Neutron-Deficient Isotopes ￣(153)Er and ￣(157)Yb

作　　者：徐树威[1] 谢元祥[1] 潘强岩[1] 张菊萍 张学谦[1] 王以好 葛元秀[1] 殷锡金[1] 王春芳[1] 张天梅[1] 刘忠[1] 郭斌[1] 罗亦孝[1] 邢正 陈星蕖 

机构地区：[1]中国科学院近代物理研究所,兰州大学现代物理系

出　　处：《高能物理与核物理》1995年第3期193-202,共10页High Energy Physics and Nuclear Physics

基　　金：中科院八五重大项目

摘　　要：利用（１６）Ｏ重离子束轰击（１４２）Ｎｄ和（１４７）Ｓｍ同位素靶分别生成（１５３）Ｅｒ和（１５７）Ｙｂ．借助氦喷嘴带传输系统和Ｘ－γ、γ－γ符合测量方法分离鉴别核素并测量其衰变性质．首次建立了（１５３）Ｅｒ和（１５７）Ｙｂ的ＥＣ／β＋衰变纲图．从中指认出（１５３）Ｈｏ的一个新三（准）粒子态和两个新单粒子态，指认出（１５７）Ｔｍ的一个新的同质异能态和一条新转动带．低位能级系统分析表明：在Ｈｏ和Ｔｍ这两条奇Ａ核的同位素链中基态形状的转变区都在中子数８６和８８之间．Er and (157)Yb were produced via xu fusion-evaporation reaction by irradiation of (142)Nd and (147)Sm with (16)O, respectively. A He-jet recoil tape transport system, X-γ and γ-γ coincidence measurements were employed to separate and identify the reaction products and to study the EC/β+ decay of (153)Er and (157)Yb. The EC/β+ decay schemes of (153)Er and (157)Yb have been proposed for the first time, from which a new three qussi-particle state and two new single proton states have been assigned to (153)Ho, and a new isomer and a new rotational band have been assigned to (157)Tm.According to systematic behaviour of the low-laying energy levels for odd holmium and odd thulium isotopes with N =82-102, it can be seen that the change from spherical to deformed shapes of nuclear ground states in the two isotope chains appears between N=86 and 88.

关 键 词：衰变纲图 铒 镱 同位素 短寿命 衰变性质 

分 类 号：O571.3[理学—粒子物理与原子核物理]