缺中子Np新核素的α衰变研究  

α Decay Studies on New Neutron-deficient Np Isotopes

作　　者：张志远[1,2] 甘再国 杨华彬[1] 马龙 黄明辉[1,2] 杨春莉[1,2] 张明明[1,2] ZHANG Zhiyuan;GAN Zaiguo;YANG Huabin;MA Long;HUANG Minghui;YANG Chunli;ZHANG Mingming(CAS Key Laboratory of High Precision Nuclear Spectroscopy,Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China;School of Nuclear Science and Technology,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院近代物理研究所高精度核谱学重点实验室,兰州730000 [2]中国科学院大学核科学与技术学院,北京100049

出　　处：《原子核物理评论》2020年第3期455-461,共7页Nuclear Physics Review

基　　金：国家自然科学基金资助项目(11975279,U1732270);中国科学院青年创新促进会项目(2020409);国家重点研发计划(2018YFA0404402);中国科学院战略性先导科技专项(B类)(XDB34010000)。

摘　　要：合成远离稳定线的新核素、探索原子核存在的极限是目前核物理研究的重要课题。在中子壳N=126的最丰质子一侧,极端缺中子的超铀核素处于质子滴线和中子壳的交叉位置,合成和研究该核区核素对研究N=126壳结构的演化性质具有重要意义。基于兰州重离子加速器上的充气反冲核谱仪装置(SHANS),利用^(36,40)Ar+^(185,187)Re熔合蒸发反应,合成了极缺中子的^(219,220,223,224)Np新核素,在中子壳N=126附近首次建立了Np同位素链的α衰变系统性,获得了N=126壳效应在Np同位素链中依然存在的实验证据。依据单质子分离能的系统性分析,确定了Np同位素链中质子滴线的位置,^(219)Np也成为目前已知的最重的质子滴线外核素。此外,基于实验测量的反应截面,并与理论模型的计算结果相比较,讨论了进一步合成该核区其它新核素^(218,221,222)Np的可行性。In contemporary nuclear research field,it is of special interest to synthesize the new isotopes far from the stability line and to explore the existing limit of nuclei.For the most proton-rich N≈126 isotones,which are located near the crossing point between the proton drip line and the N=126 closed shell,synthesizing and α-decay studies may shed new light on the structural evolution of the N=126 shell closure.Based on measurements at the gas-filled recoil separator SHANS,the most neutron-deficient new isotopes,^(219,220,223,224)Np,were synthesized via^(36,40)Ar+^(185,187)Re fusion-evaporation reactions.The new experimental results allow us to establish the α-decay systematics for Np isotopes around N=126 for the first time,and to test the robustness of this shell closure in neptunium.The systematic analysis of single proton separation energies figures out the exact location of the proton drip line in Np isotopic chain.At the same time,the isotope ^(219)Np was identified as the presently known heaviest nuclide beyond the proton drip line.In addition,the possibility of producing other new isotopes^(218,221,222Np) in this region is discussed in terms of the measured cross sections and the theoretical predictions.

关 键 词：新核素 充气反冲核谱仪 α衰变系统性 壳结构演化 反应截面 

分 类 号：O571.22[理学—粒子物理与原子核物理]