Nuclear spectroscopic studies of neutron-rich nuclei far from stability

利用在线同位素分离器KUR-ISOL对富中子裂变产生的核进行了核光谱研究。本资助项目制备了新型高温离子源、大型Si（Li）探测器和数据采集系统，并有效地用于以下研究：1)在^<235>U的裂变产物中发现了一个nwe同位素^<156>Pm。34条新的射线线被分配给这个同位素。2)发现了一种新的同位素^<155>Nd。该同位素的半衰期为9.5 ~ 0.7 s，有4条射线线。3)最近发现了稀土元素的新同位素^<154>Pr，其束强增加了。该同位素的半衰期为2.3 0.1 s，并发现了10条新的射线线。4)对过渡核^<147>Ba、^<147>La和^<147>Ce进行了核光谱研究。对内部转换电子和射线进行了精确测量，并确定了许多新的谱线和能级。数据分析正在进行中。目前，我们正在进一步改进离子源和撇光器系统，使光强提高数倍。对新同位素和极富中子同位素的进一步研究将继续深入了解远离稳定的原子核的核结构。

Nuclear spectroscopic studies on neutron-rich fission-produced nuclei have been performed using the on-line isotope separator KUR-ISOL. A new type high-temperature ion source, a large Si(Li) detector and a data aquisition system have been prepared by this grant-in-aid and have effectively been used for the following studies:1) A nwe isotope ^<156>Pm has been discovered among the fission products of ^<235>U. 34 new -ray lines have been assigned to this isotope.2) A new isotope ^<155>Nd has been discovered. The half-life was determined as 9.5 0.7 s and 4 -ray lines have been assigned to this isotope.3) A new isotope ^<154>Pr has recently been discovered with increased beam intensity of KUR-ISOL for rare-earth elements. The half-life is 2.3 0.1 s and 10 new -ray lines have been identified to originate from this isotope.4) Nuclear spectroscopic studies have been performed on the transitional nuclei ^<147>Ba, ^<147>La and ^<147>Ce. Internal conversion electrons and -rays have been precisely measured and a lot of new lines and levels have been identified. The data analyses are now in progress.We are now further improving the ion source and skimmer system to increase the beam intensity of ISOL several times. Further studies on new isotopes and on extremely neutron-rich isotopes will be continued to a deep understanding of nuclear structure of nuclei far from stability.