Gammasphere上裂变丰中子核核结构若干前沿领域的新进展(Ⅰ:第一和第二部分)(英文)  

New Insights into Frontier of Nuclear Structure of Neutron-rich Nuclei by Means of Prompt Fission γ Ray Measurements at Gammasphere(Ⅰ: Section 1 & Section 2)

作　　者：罗亦孝 J.H.Hamilton J.O.Rasmussen A.V.Ramayya C.Goodin A.V.Daniel N.J.Stone 朱胜江 J.K.Hwang 刘少华 C.J.Beyer 李科 H.L.Crowell D.Almehed S.Frauendorf A.Covello V.Dimitrov 张敬业 车兴来 姜卓 D.Fong A.Gelberg I.Stefanescu A.Gargano E.F.Jones P.M.Gore I.Y.Lee G.M.Ter-Akopian Yu.Ts.Oganessian M.A.Stoyer R.Donangelo 马文超 J.D.Cole J.Kormicki 张学谦 S.C.Wu J.Gilat T.N.Ginter S.J.Asztalos 

机构地区：[1]Physics Department,Vanderbilt University,Nashville [2]Lawrence Berkeley National Laboratory,Berkeley [3]Flerov Laboratory for Nuclear Reactions,JINR,Dubna [4]Joint Institute for Heavy Ion Research,Oak Ridge [5]Department of Physics,Oxford University [6]Department of Physics and Astronomy,University of Tennessee,Knoxville [7]Physics Department,Tsinghua University [8]Department of Physics,University of Notre Dame,Notre Dame [9]Institut für Strahlenphysik,FZD-Rossendorf [10]Dipartimento di Scienze Fisiche,Universita di Napoli Federico II,and Istituto Nazionale di Fisica Nuclear,Complesso Universitario di Monte S.Angelo,Via Cintia [11]Idaho Accelerator Center,Idaho State University [12]Institut für Kernphysik,Universitt zu Kln [13]Department of Chemistry and Biochemistry,University of Maryland [14]Dipartimento di Scienze Fisiche,Universita di Napoli Federico II,and Istituto Nazionale di Fisica Nuclear,Complesso Universitario di Monte S.Angelo [15]Lawrence Livermore National Laboratory,Livermore [16]Instituto de Física,Facultad de Ingeniería [17]Mississippi State University,Drawer 5167,Mississippi State [18]Idaho National Laboratory,Bldg.IRCPL [19]Department of Physics,National Tsing Hua University,Hsinchu [20]National Superconducting Cyclotron Laboratory,Michigan State University,East Lansing [21]Massachusetts Institute of Technology,Cambridge

出　　处：《原子核物理评论》2010年第3期229-251,共23页Nuclear Physics Review

基　　金：US Depart ment of Energy Grants(DE-FG05-88ER40407,DE-FG02-96ER40983,DE-FG02-95ER40093);Contract(W-7405-ENG48,DE-AC03-76SF00098,DE-AC07-76ID01570);The Work at Tsinghua University was supported by National Natural Science Foundation of China(10575057,10775078);Major State Basic Research Development Program of China(2007CB815005)~~

摘　　要：(第一和第二部分):使用Gammasphere多探测器系统对252Cf裂变源瞬发γ射线进行γ-γ-γ和γ-γ(θ)符合测量,裂变丰中子原子核核结构若干前沿领域的深入研究获得了新的进展。高达5.7×1011以上的三重和更高重符合事件的数据统计,以及更少压缩的三维数据为宽广未知丰中子核区的寻找和研究提供了有利的条件。在具有重要物理意义的若干丰中子核区首次建立,或显著扩展了一批包括转晕态和转晕附近能态的高自旋能级纲图。在偶-偶丰中子核110,112Ru和108Mo中鉴别出了手征对称破缺结构。丰中子110,112Ru附近核的三轴形变基态具有最低的能量,在它们之中已确认了接近最大值的三轴形变。在这些Ru和Mo同位素中观察到的手征双线能带展示出手征破缺的一切特征,特别是其理想的能量简并,表明它们在迄今已报道的手征破缺结构中,具有最好的手征特性。研究了手征结构从具有γ软度的108Ru到具有大三轴形变的110,112Ru的过渡。斜轴推转(TAC)和随机相近似(RPA)理论计算成功地拟合了在这些偶-偶丰中子核中观察到的手征双线能带的特性,并指定其为软手征振动态。在这些偶-偶核中观察到的手征破缺不可能归纳为奇-奇核中那样的简化的几何图像。前者来自闭壳外所有中子的相互作用。对双幻核132Sn附近N=83同中素链的系统研究为这个极富吸引力的核区提供了大量新的谱学信息。N=83同中素135Te(Z=52),136I(Z=53),137Xe(Z=54),138Cs(Z=55)和139Ba(Z=56)的最新能级信息,特别是首次建立的138Cs高自旋能级纲图和壳模型理论计算表明,Z=50质子闭壳外少数g7/2价质子激发同N=82中子闭壳外之唯一f7/2价中子的耦合对该核区能级结构具有关键作用。观察到了132Sn和208Pb附近核区谱学信息的相似性和相对应的三粒子和五粒子态。在135Te中观察到了磁转动,这是在双幻核132Sn附近观察到的首例磁转动。（Section 1 and Section 2）：New insights have been gained into the frontiers of nuclear structure of neutron-rich nuclei by means of γ-γ-γ and γ-γ（θ） coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf at Gammasphere.Over 5.7×1011 triple-and higher-fold coincidence events and the less-compressed cube data provide excellent conditions for searches and studies over a wide unknown range with more neutron excess.High-spin yrast and near yrast level schemes of neutron-rich nuclei in regions of physics interest have been identified for the first time,or extensively extended and expanded compared to previous preliminary measurements.Chiral symmetry breaking was recently identified in even-even neutron-rich 110,112Ru and 108Mo isotopes.The former have the largest lowering of ground state energy when axial symmetry is broken,and near maximum triaxiality was deduced in the isotopes.By exhibiting all the fingerprints for chiral doubling,especially the best energy degeneracy,the doublet bands observed in these Ru and Mo isotopes are the best examples of chiral properties reported in this region.The evolution of chirality from γ-soft 108Ru to triaxial 110,112Ru is proposed.Tilted axis cranking（TAC） calculations extended by random phase approximation（RPA） calculations can explain the features of the doublet bands in terms of a soft chiral vibration for these even-even nuclei.The chirality in these even-even nuclei cannot be reduced to the simple geometrical picture as in odd-odd nuclei.Instead,in these even-even nuclei the tendency to chirality comes about from the interplay of all the neutrons in the open shell.Systematic studies of the N=83 isotonic chain in the vicinity of the doubly-magic 132Sn have yielded a wealth of spectroscopic information in this attractive region.The new data of N=83 isotones 135Te（Z=52）,136I（Z=53）,137Xe（Z=54）,138Cs（Z=55） and 139Ba（Z=56）,especially the observation of the long-sought level scheme of 138Cs,and shell model calculations,

关 键 词：(第一和第二部分):丰中子核 高自旋 转晕态 裂变 252Cf γ射线三重符合 角关联 Gammasphere多探测器系统 手征对称破缺 三轴形变 斜轴推转(TAC)计算 软手征振动 N=83同中数链 双幻核132Sn 壳模型计算 磁转动 谱学相似性 

分 类 号：O572.33[理学—粒子物理与原子核物理]