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Previous experimental results of (EC+β+) decay for the medium-heavy nuclei reported by our group since 1996, including 153Er, 157Yb, 209Fr, 128Ce, 130Ce, and 128Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion. 相似文献
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利用187 MeV的40Ca离子轰击同位素靶92Mo, 由熔合蒸发反应生成目标核126Ce。 藉助氦喷嘴快速带传输系统和X-X-t与X-γ-t符合测量, 首次建立了126Ce的EC/β+衰变纲图。 建议了可能属于126Ce一个高自旋同核异能态的衰变, 其β衰变后布居在与126La的高自旋同核异能态相关的低位能级区, 测定的半衰期是57(9) s。 也建议了可能属于126Ce基态的衰变, 其β衰变后布居在与126La的低自旋同核异能态相关的低位能级区,它的半衰期被测定为12(4) s。 但偶偶核126Ce存在高自旋同核异能态的物理原因还有待进一步探究。 Ce was produced by bombarding an enriched target of 92Mo with 187 MeV 40Ca beam and studiedby using a helium jet fast tape transport system in combination with X-γ and γ-γ coincidencemeasurements. An EC/β+ decay scheme of 126Ce was proposed for the first time. A group of low lying states associated with the low spin isomer in 126La feeding by β decay was possibly from the ground state EC/β+ decay of 126Ce with the measured half-life 12(4) s. Another group of low lying states associated with the high spin isomer in 126La feeding by β decay was possibly from a high spin isomer EC/β+ decay of 126Ce with the measured half-life 57(9) s. However, the physical reason for the existence of a high spin isomer in even-even nucleus 126Ce is still an open problem. 相似文献
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通过96 Ru( 4 0 Ca ,ln2p)反应 ,采用氦喷嘴带传输系统和X γ与γ γ符合测量方法 ,首次建议了133Sm的简单的 (EC + β+)衰变纲图 .由于Ru靶中含有98— 10 2 Ru的成分 ,同时产生了133Pr,并首次测定了133Pr的 1 1 / 2 - 同质异能态的寿命为( 1 .1± 0 .2 )s.用单粒子模型提取了131,133,135 ,137Pr的 1 1 / 2 - 同质异能态的约化跃迁几率的实验值 ,并与Weisscopf近似估计进行了比较 . 相似文献
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楼建玲 李智焕 叶沿林 江栋兴 华辉 李湘庆 张双全 郑涛 葛愉成 孔赞 吕林辉 李琛 卢飞 范凤英 李忠宇 曹中鑫 马立英 Faisal 徐瑚珊 胡正国 王猛 雷相国 段利敏 肖志刚 黄天衡 付芬 章学恒 郑川 余玉洪 涂小林 张亚鹏 杨彦云 张宏斌 唐彬 田育林 欧阳珍 黄美容 徐治国 岳珂 高启 《中国物理 C》2008,32(Z2):41-43
The β-delayed neutron and γ spectra of neutron-rich nucleus 21N using β-γ and β-n coincidence measurements were presented in this paper. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio 88.7±4.2% were observed. One γ transition among the excited states of 21O, and four γ transitions among the excited states of 20O were identified in the β decay chain of 21N. The ungated half-life of 83.8±2.1 ms was also determined for 21N. 相似文献
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利用102MeV16O6+束轰击同位素靶117Sn,通过熔合蒸发4n反应产生核素129Ce.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129Ce.基于X–γ–t和γ–γ–t符合测量,建议了包括51条射线在内的129Ce的(EC/β+)衰变纲图.其中,129Ce基态直接馈送到129La基态的份额(26±7)%是用观测到的129La衰变的278.6keV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68.2keVγ射线开门的γ谱以及典型的衰变γ射线的时间谱. 相似文献
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利用能量为170MeV左右的36Ar重离子束轰击96Ru和106Cd浓缩同位素靶,分别生成缺中子同位素130Nd和140Tb.借助氦喷嘴带传输系统,用 X-γ和 γ-γ符合方法,分离鉴别了这两种核素,并进一步测定了它们的衰变性质.得到130 Nd的半衰期为(13± 3)s,首次建议了它的EC/β+衰变纲图,推测了其子核130Pr的基态和低位能级的自旋宇称.修订了140Tb的原有极简单的EC/β+衰变纲图并指认140Tb的基态自旋宇称为7+. 相似文献
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HUA Hui LI ZhiHuan YE YanLin JIANG DongXing LOU JianLing LI XiangQing & XU FuRong School of Physics State Key Laboratory of Nuclear Physics Technology Peking University Beijing China 《中国科学:物理学 力学 天文学(英文版)》2011,(Z1)
The β-decay studies of neutron-rich 18,21N isotopes have been performed using β-n, β-γ, and β-n-γ coincidence methods. The 18,21N ions were produced by the fragmentation of the 22Ne and 26Mg beams, respectively, on a thick beryllium target. The time of flight of the emitted neutrons following the β-decay of 18,21N was measured by a neutron detector system with wide energy detection range and low-energy detection threshold. In addition, several clover germanium detectors were used to detect the β-delayed γ-r... 相似文献
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在210MeV的束流能量下, 利用重离子熔合蒸发反应146Nd(35Cl, 5nγ)176Ir产生具有β+/EC衰变性质的核素176Ir,由氦喷嘴快速带传输系统将反应产物传送到低本底区进行测量. 经过实验数据的离线处理分析,对早先发表的176Ir衰变γ跃迁进行确认的同时又发现了3个新能级和10条新的γ射线, 丰富了176Os核的低位激发态能级纲图. 并根据典型γ射线的衰变时间谱建议了176Ir核的一个长寿命的低自旋同核异能态. 相似文献
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The π+π- transition of heavy quarkonia in decay ψ(2S) ψ(2S)→π+π-J/ψ is studied. With the BESII data on the decay ψ(2S)→π+π-J/ψ, we update the values of coupling constants (gi) and chromopolarizability (аψ(2S)J/ψ) in this process. 相似文献
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利用能量为170MeV左右的36Ar重离子束轰击96Ru和106Cd浓缩同位素靶,分别生成缺中子同位素130Nd和140Tb.借助氦喷嘴带传输系统,用X–γ和γ–γ符合方法,分离鉴别了这两种核素,并进一步测定了它们的衰变性质.得到130Nd的半衰期为(13±3)s,首次建议了它的EC/β+衰变纲图,推测了其子核130Pr的基态和低位能级的自旋宇称.修订了140Tb的原有极简单的EC/β+衰变纲图并指认140Tb的基态自旋宇称为7+. 相似文献
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Motivated by the rst measurement on B(Bs→φμ+μ-) by the CDF Collaboration, we study the supersymmetric e ects in semi-leptonic Bs→φμ+μ- decay. In our evaluations, we analyze the dependences of the dimuon invariant mass spectrum and the forward-backward asymmetry on relevant supersymmetric couplings in the MSSM with and without R-parity. The analyses show that the new experimental upper limits of B(Bs→φμ+μ-)from the LHCb Collaboration could further improve the bounds on sneutrino exchange couplings and (δLLu)23 as well as (δLL,RRu)23 mass insertion couplings. In addition, within the allowed ranges of relevant couplings under the constraints from B(Bs→φμ+μ-), B(B→K(*)μ+μ-) and (Bs→φμ+μ-), the dimuon forward-backward asymmetry and the di erential dimuon forward-backward asymmetry of Bs→φμ+μ-are highly sensitive to the squark exchange contribution and the (δLLu)23 mass insertion contribution. The results obtained in this work will be very useful in searching for supersymmetric signals at the LHC. 相似文献
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利用16O重离子束轰击142Nd和147Sm同位素靶分别生成153Er和157Yb.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153Er和157Yb的EC/β+衰变纲图.从中指认出153Ho的一个新三(准)粒子态和两个新单粒子态,指认出157Tm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. 相似文献
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本文简单介绍了首次成功地测定这两个衰变纲图的技术难点、实验过程、主要实验结果及物理意义。 EC/β+ decay schemes of 153Er and 157Yb are proposed for the first time. The related technical difficulty, experimental process, main results and their physics are representedbrigly. 相似文献
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Experimental data of nuclear β+-decay half-lives are systematically analyzed and investigated. We present an exponential law between the half-life of β+-decay with the same forbiddenness and the nucleon number (Z,N) of parent nucleus far from the β-stable line. A formula with four parameters is proposed to describe the β+-decay half-lives of nuclei far from stability. Experimental β+-decay half-lives of the first and second forbidden transitions are well reproduced by this simple formula. The physics of the exponential law is related to the statistical properties of β+-decay far from β-stable line. 相似文献
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1 Introduction The production of nuclear spin polarization and the maintenance of the nuclear po-larization in a stopper are the essential requirement for the measurement of nuclear magnetic and electric quadrupole moments of the b-emitting nuclei by the ?NMR and b-NQR (b-ray detected Nuclear Magnetic Resonance and b-ray detected Nuclear Quad-rupole Resonance) technique. This requirement can be realized by the selection tech-nique of the incident particle energy of the nuclear reaction th… 相似文献