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)

原子核物理评论 , 2010, 27(3): 229-251.

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)

罗亦孝 ^1, , J.H.Hamilton ^2, , J.O.Rasmussen ^3, , A.V.Ramayya ^4, , C.Goodin ^5, , A.V.Daniel ^6, , N.J.Stone ^7, , 朱胜江 ^8, , J.K.Hwang ^9, , 刘少华 ^10, , C.J.Beyer ^11, , 李科 ^12, , H.L.Crowell ^13, , D.Almehed ^14, , S.Frauendorf ^15, , A.Covello ^16, , V.Dimitrov ^17, , 张敬业 ^18, , 车兴来 ^19, , 姜卓 ^20, , D.Fong ^21, , A.Gelberg ^22, , I.Stefanescu ^23, , A.Gargano ^24, , E.F.Jones ^25, , P.M.Gore ^26, , I.Y.Lee ^27, , G.M.Ter-Akopian ^28, , Yu.Ts.Oganessian ^29, , M.A.Stoyer ^30, , R.Donangelo ^31, , 马文超 ^32, , J.D.Cole ^33, , J.Kormicki ^34, , 张学谦 ^35, , S.C.Wu ^36, , J.Gilat ^37, , T.N.Ginter ^38, , S.J.Asztalos ^39,

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基金项目: 中国国家自然科学基金(10575057;10775078) 合同资助项目(W-7405-ENG48;DE-AC03-76SF00098;DE-AC07-76ID01570) 国家重点基础研究发展规划资助项目(2007CB815005) 美国能源部基金(DE-FG05-88ER40407;DE-FG02-96ER40983;DE-FG02-95ER40093)

关键词：丰中子核 , 高自旋 , 转晕态 , 裂变 , 252Cf , γ射线三重符合 , 角关联 , Gammas-phere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

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

Keywords： neutron-rich nuclei , high spin , yrast , fission , 252Cf , γ-γ-γand γ-γ(θ) coincidences , Gammasphere , chiral symmetry breaking , triaxiality , tilted axis cranking (TAC)calculations , soft chiral vibration , N=83 isotonic chain , doubly-magic 132Sn , shell model calculati ,

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),134I(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 emit-ted in the spontaneous fission of 252Cf at Gammasphere. Over 5.7×1011 triple-and higher-fold co-incidence 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 110,112 Ru and 108 Mo isotopes. The former have the largest lowering of ground state energy when axial symmetry is bro-ken, 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 108 Ru to triaxial110, 212 Ru is proposed. Tilted axis cranking (TAC) calculations extended by random phase approximation (RPA) calculations can explain the features of the dou-blet 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 iso-tones135Te (Z=52), 136>I (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, indicate the key role played by the coupling of the excitations of the few g7/2 valence protons outside the Z= 50 major shell closure and the f7/2 valence neutrons outside the N=82 major shell closure. Resem-blance of spectroscopy and counterparts were observed between the 132 Sn region and 208Pb region.Tilted rotation(magnetic rotation) was observed in 135 Te, which is the first observation of magne-tic rotation in the vicinity of 132Sn.

参考文献

[1]	Hamilton J H,Ramayya A V,Zhu S J,et al.Prog Part Nucl Phys,1995,35:635.
[2]	Zhang C T,Bhattacharyya P,Daly P J,et al.Phys Rev Lett,1996,77:3743.
[3]	Baxter A M,Khoo T L,Bleich M E,et al.Nucl Inst and Meth,1992,A317:101.
[4]	Radford D C.Nucl Inst and Meth,1995,A317:297,also cf.his website httpt://radware,phy.ornl.gov/.
[5]	Hamilton J H,TerAkopian G M,Oganessian Y T,et al.Phys Rep,1996,264:215.
[6]	Wu S C,Donangelo R,Rasmussen J O,et al.Phys Rev,2000,C62:041601.
[7]	Daniel A V,Goodin C,Li K,et al.Nucl Instr and Meth,2007,B262:399.
[8]	Frauendorf S,Meng J.Nucl Phys,1997,A617:131.
[9]	Frauendorf S.Rev Mod Phys,2001,73:463.
[10]	Koike T,Starosta K,Hamamoto I,et al.Phys Rev Lett,2004,93:172502.
[11]	Vaman C,Fossan D B,Koike T,et al.Phys Rev Lett,2004,92:032501.
[12]	Starosta K,Koike T,Chiara C J,et al.Phys Rev Lett,2001,86:971.
[13]	Dimitrov V I,Frauendorf S.Proc.Third Int.Conf.Fission and Properties of Neutron-rich Nuclei.In:Hamilton J H ed.Singapore:World Scientific,2003,93.
[14]	Hecht A A,Beausang C W,Zyromski K E,et al.Phys Rev,2001,C63:051302.
[15]	Starosta K,Chiara C J,Fossan D B,et al.Phys Rev,2001,C63:061304.
[16]	Starosta K,Chiara C J,Fossan D B,et al.Phys Rev,2002,C65:044328.
[17]	Mergel E,Petrache C M,Lo Bianco G,et al.Eur Phys J,2002,A15:417.
[18]	Zhu S,Garg U,Nayak B K,et al.Phys Rev Lett,2003,91;132501.
[19]	Grodner E,Srebrny J,Pasternak A A,et al.Phys Rev Lett,2000,97:172501.
[20]	Koike T,Starosta K,Chiara C J,et al.Phys Rev.2003,C67:044319.
[21]	Timar J,Joshi P,Starosta K,et al.Phys Lett,2004,B598,178.
[22]	Joshi P,Jenkins D G,Raddon P M,et al.Phys Lett,2004,B595:135.
[23]	Timar J,Vaman C,Starosta K,et al.Phys Rev,2006,C73:011301(R).
[24]	Joshi P,Wilkinson A R,Koike T,et al.Eur Phys J,2005,A24:23.
[25]	Zhu S J,Hamilton J H,Ramayya A V,et al.Eur Phys J,2005,A25:459.
[26]	Joshi P,Carpenter M P,Fossan D B,et al.Phys Rev Lett,2007,98:102501.
[27]	Petrache C M,Hagemann G B,Hamamoto I,et al.Phys Rev Lett,2006,96:112502.
[28]	Tonev D,de Angelis G,Brant S,et al.Phys Rev,2007,C76:044313.
[29]	Mukhopadhyay S,Almehed D,Garg U,et al.Phys Rev Lett,2007,99:172501.
[30]	Luo Y X,Zhu S J,Hamilton J H,et al.Phys Lett,2009,B670:307.
[31]	Luo Y X,Zhu S J,Hamilton J H,et al.Intern Jour of Moder Phys,2009,E18(8):1697.
[32]	Aysto J,Jauho P P,Janas Z,et al.Nucl Phy,1990,A515:365.
[33]	Luo Y X,wu S C.Gilat J,et al.Phys Rev,2004,C69:024315.
[34]	Luo Y X,Rasmussen J O,Hamilton J H,et al.Phys Rev,2004,C70:044310.
[35]	Luo Y X,Rasmussen J O.Stefanescu I,et al.J Phys,2005,G31:1303.
[36]	Luo Y X,Hamilton J H,Rasmussen J O,et al.Phys Rev,2006,C74:024308.
[37]	Moller P,Bengtsson R,Carlsson B G,et al.Phys Rev Lett,2006,93:162502.
[38]	Stefaneseu I,Gelberg A,Jolie J,et al.Nucl Phys,2007,789:125.
[39]	Zhu S J,Luo YX,Hamilton J H,et al.Intern Jour of Moder Phys,2009,E18(8):1717.
[40]	Almehed D,Frauendorf S.Submitted Phys Rev C,arXiv:0709:0969
[41]	Baranger M,Kumar K.Nuc Phys,1968,A110:490.
[42]	Almehed A,Frauendorf S.to be published.
[43]	Blomqvist J.In Proceedings of the 4th Inter Conf on Nucl Far From Stability,Helsingoer:Denmark,1981,536.
[44]	Firestone R B,Shirley V S.Table of Isotopes,8th ed,New York:Wiley,1996.
[45]	Prade H,Enghardt W,Dioszegi I,et al.Nucl Phys,1987,A472:381.
[46]	Bhattacharyya P,Zhang C T,Fornal B,et al.Phys Rev,1997,C56:R2363.
[47]	Daly P J,Bhattacharyya P,Zhang C T,et al.Phys Rev,1999,C59:3066.
[48]	Li K,Luo Y X,Hwang J K,et al.Phys Rev,2007,C75:044314.
[49]	Luo Y X,Rasmussen J O,Hamilton J H,et al.In Fission and Properties of Neutron-rich Nuclei.In:Hamilton J H,Ramayya,A V,Carter H K.Proceedings of the 3rd International Conference,Sanibel Island,Florida,USA,Singapore:World Scientific,2003,310.
[50]	Luo Y X,Rasmussen J O,Ramayya A V,et al.Phys Rev,2001,C64:054306-1.
[51]	Hwang J K,Ramayya A V,Hamilton J H,et al.Phys Rev,2004,C69:057301.
[52]	Urban W,Sarkar M S,Sarkar S,et al.Eur Phys J,2006,A27:257.
[53]	Fornal B,Broda R,Krolas W,et al.In Proceedings of the International Conference on Nuclear Physics Close to the Barrier,Warszawa,Poland,(June 30,1998),Acta Physica Polonica,1999,B30(5):1219.
[54]	Fornal B,Broda R,Krolas W,et al.In Proceedings of the International Conference on Nuclear Physics Close to the Barrier,Warszawa,Poland,(June 30,1998),Acta Physica Polonica,1999,B30(5):1219.
[55]	Fornal B,Broda R,Daly P J,et al.Phys Rev,2001,C63:024322.
[56]	Baldsiefen G,Hubel H,Korten W G,et al.Nucl Phys,1944,A574:521.
[57]	Frauendorf S.Nucl Phys,1993,A557:259c;ibid,2000,A677:115.
[58]	Frauendorf S.Nucl Phys,1993,A557:259c;ibid,2000,A677:115.
[59]	Frauendorf S.Z Phys,1997,A358:153.
[60]	Machleidt R.Phys Rev,2001,C63:024001.
[61]	Covello A,Manfredi V R,Azziz N,et al.to be published,available online at www.sciencedirect.com.
[62]	Liu S H,Hamilton J H,Ramayya A V,et al.Phys Rev,2009,C80:044314.
[63]	Luo Y X,Rasmussen J O,Hamition J H,et al.Nucl Phys,2010,A823:1
[64]	Liu S H,Hamilton J H,Ramayya A V,et al.Phys Rev,2010,C81:037302.
[65]	Liu S H,Hamiltion J H,Ramayya A V,et al.Phys Rev,2010,C84:057304.
[66]	Coraggio L,et al.Unpublished.
[67]	Stuchbery A E,Dracoulis G D,Byrne A P,et al.Nucl Phys,1988,A482:692.

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