An angular momentum projected potential-energy-surface （PES） calculation, which takes both rotational symmetry restoration and multi-quasiparticle excitation into account, is developed by using the macroscopic-micro...An angular momentum projected potential-energy-surface （PES） calculation, which takes both rotational symmetry restoration and multi-quasiparticle excitation into account, is developed by using the macroscopic-microscopic model and the projected shell model （PSM）. Within this method, it may become possible to modify the excitation spectra which are influenced by shape-softness of nuclei, including high-K states. As our first example, this method is adopted to study the collective and multi-quasiparticle excitations of 178Hf~ and the results are in good agreement with the existing experimental data. In addition, as for the dominant structure of non- collective 6＋ bands, the conflict between experimental result and the previous PSM calculation is clarified.展开更多
In the framework of the projected shell model, we investigate the competition between the two-quasineutron and two-quasiproton K~π=6~＋ states in the ytterbium isotopes and N =104 isotones adjacent to ^（174）Yb. Th...In the framework of the projected shell model, we investigate the competition between the two-quasineutron and two-quasiproton K~π=6~＋ states in the ytterbium isotopes and N =104 isotones adjacent to ^（174）Yb. The ^（174）Yb results are compared with the experimental data.The K~π =6~＋ isomer observed in ^（174） Yb is assigned as an admixture of the ν7/2^-[514] ν5/2^-[512] and π7/2~＋ [404]π5/2~＋ [402] intrinsic structure, which explains the experimental ｜g K-g R ｜ value. Similar mixing would appear in ^（174） Yb, ^（176） Hf,and ^（178） W. The low-lying K~π=6~＋ states are also predicted in ^（170-178） Yb.展开更多
基于Ru(Z=44)丰中子同位素中存在最大三轴形变的理论预言和实验证据,综述了近年来Rh(Z=45),Pd(Z=46),Ag(Z=47),Cd(Z=48)(质子数Z位于Ru,Z=44之上)及Zr(Z=40),Nb(Z=41),Mo(Z=42),Tc(Z=43)(质子数Z位于Ru,Z=44之下)的A～(100～126)丰中子...基于Ru(Z=44)丰中子同位素中存在最大三轴形变的理论预言和实验证据,综述了近年来Rh(Z=45),Pd(Z=46),Ag(Z=47),Cd(Z=48)(质子数Z位于Ru,Z=44之上)及Zr(Z=40),Nb(Z=41),Mo(Z=42),Tc(Z=43)(质子数Z位于Ru,Z=44之下)的A～(100～126)丰中子同位素中关于三轴形变的形状变迁和形状共存系统性研究的重要进展。252Cf自发裂变瞬发γ射线γ-γ-γ三重符合、特别是新建立的γ-γ-γ-γ四重符合数据的系统观测和研究,在Ru,Pd,Cd和Nb丰中子同位素中显著扩展或首次观测到了一系列能带,为这个核区原子核形状的研究提供了新的、重要的实验数据。联系此前报道的有关进展,使用PES,TRS,PSM,CCCSM和SCTAC理论模型计算拟合新的实验数据,在该核区沿同中素和同位素链,并随自旋和激发能变化各自由度,跟踪原子核形状渐进变化,获得了新的系统性研究成果,显著扩展和深化了人们对原子核形状变迁和形状共存的认知。对于Ru及其上的Rh(Z=45),Pd(Z=46),Ag(Z=47)和Cd(Z=48)丰中子同位素的研究表明:Rh丰中子核具有比最大值稍小的三轴形变,γ=-28°,并在103–106Rh同位素链上鉴别出了手征对称破缺;在三轴形变核112Ru和114Pd(N=68)中发现了三轴原子核的摆动运动,该摆动运动也可能在114Ru(N=70)中存在;观察到了从具有最大三轴形变的110,112Ru中手征破缺到稍小三轴形变的112,114,116Pd中扰动的手征破缺的过渡;在较软的Ag核中观察到了丰富的谱学结构,在104,105Ag中鉴别出了可能的手征对称破缺,在较重的115,117Ag中提出了趋于三轴形变的γ软度;具有小形变的Cd核的能级结构被解释为准粒子耦合、准转动和软三轴形变;最近的库伦激发的研究提供了Z=50,N=82满壳附近122,124,126Cd核中出现核集体性的实验和理论证据;上述研究成果展现出从Ru中的最大三轴形变(γ=-30°,三轴形变极小增益为0.67 Me V),经具有大三轴形变的Rh核(γ=-28°),到Pd核中的稍小、但稳定于中等自旋到高自旋区的三轴形变(γ～-41°,三轴形变极小增益为0.32 Me V),再经Ag核中的γ软度,最后到具有很小形变、但仍出现集体性质、包括软三轴形变的Cd核的过渡。对于Pd核转动带交叉系统性的研究揭示了其第一带交叉(νh11/2)2中子转动顺排的上行γ驱动,和第二带交叉(πg9/2)2质子转动顺排的下行γ驱动效应,成功地解释了114Pd中的三轴摆动运动,并给出了110-118Pd同位素链中理论早已预言、而比早期理论预言更为完整准确的形状渐进变迁和形状共存的图像。根据该核区的系统研究,发现最大三轴形变出现在112Ru,而在相邻的偶Z(Pd)同位素链,三轴形变极小的中心在114Pd,两者均为N=68。上述系统性研究沿相邻的Ru和Pd偶Z同位素链,在N=68同中素中鉴别出最大三轴形变,均比理论预言的108Ru和110Pd多4个中子。在Z值位于Ru(Z=44)之下的Zr(Z=40),Nb(Z=41),Mo(Z=42)and Tc(Z=43)丰中子同位素中,Y和Zr核具有很强的轴对称四极形变,而在较重的Zr同位素中出现了γ自由度;较重的Nb核(A=104～106)基态具有中等程度的软三轴形变和强四极形变,随着自旋和激发能的增加,过渡到接近于轴对称的强四极形变;而较轻的Nb核(A 103)基态均接近轴对称形状;在Nb同位素链上基态由球形到强四极形变的形状突变发生在100Nb(N=59),在100–106Nb同位素链中基态的软三轴形变随中子数增加而增加;在Nb核中还观察到关于软三轴形变的形状共存;Mo核具有大的三轴形变,观察到了γ振动和手征对称破缺;Tc核具有比最大值稍小的三轴形变,γ=-26°,并观察到了手征对称破缺。质子数Z从41到48的A～(100～126)丰中子同位素,特别是Pd和Nb同位素,呈现出关于三轴形变的过渡特征。展开更多
Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in...Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in 72Kr to prolate in 74,76Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0＋ states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes （except the ground state of 72Kr）, the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed.展开更多
Configuration-constrained potential-energy-surface calculations have been performed to investigate the K isomerism in the proton-rich A～ 80 mass region. An abundance of high-K states are predicted. These high-K state...Configuration-constrained potential-energy-surface calculations have been performed to investigate the K isomerism in the proton-rich A～ 80 mass region. An abundance of high-K states are predicted. These high-K states arise from two and four-quasi-particle excitations, with K^π= 8^＋ and K^π= 16^＋, respectively. Their excitation energies are comparatively low, making them good candidates for long-lived isomers. Since most nuclei under study are prolate spheroids in their ground states, the oblate shapes of the predicted high-K states may indicate a combination of K isomerism and shape isomerism.展开更多
基金supported by Natural Science Foundation of China (Nos. 10735010, 10975006)the Chinese Major State Basic Research Development Program (No. 2007CB815000)
文摘An angular momentum projected potential-energy-surface （PES） calculation, which takes both rotational symmetry restoration and multi-quasiparticle excitation into account, is developed by using the macroscopic-microscopic model and the projected shell model （PSM）. Within this method, it may become possible to modify the excitation spectra which are influenced by shape-softness of nuclei, including high-K states. As our first example, this method is adopted to study the collective and multi-quasiparticle excitations of 178Hf~ and the results are in good agreement with the existing experimental data. In addition, as for the dominant structure of non- collective 6＋ bands, the conflict between experimental result and the previous PSM calculation is clarified.
基金Supported by National Natural Science Foundation of China (10975006)
文摘In the framework of the projected shell model, we investigate the competition between the two-quasineutron and two-quasiproton K~π=6~＋ states in the ytterbium isotopes and N =104 isotones adjacent to ^（174）Yb. The ^（174）Yb results are compared with the experimental data.The K~π =6~＋ isomer observed in ^（174） Yb is assigned as an admixture of the ν7/2^-[514] ν5/2^-[512] and π7/2~＋ [404]π5/2~＋ [402] intrinsic structure, which explains the experimental ｜g K-g R ｜ value. Similar mixing would appear in ^（174） Yb, ^（176） Hf,and ^（178） W. The low-lying K~π=6~＋ states are also predicted in ^（170-178） Yb.
基金US Department of Energy(DE-FG-05-88ER40407,DE-AC02-05CH11231,DE-FG02-95ER40934,DE-AC05-00OR22725,DE-AC52-07NA27344,DE-FG02-95ER40939)National Natural Science Foundation of China(11175095,10975082,11235001,11320101004,11305059,11275063,11275068,11135005,11075103)+2 种基金Special Program of Higher Education Science Foundation(2010000211007)National Basic Research Program of China(973 Program)(2013CB834401)Russian Foundation for Basic Research(11-02-12050,11-02-12066)~~
文摘基于Ru(Z=44)丰中子同位素中存在最大三轴形变的理论预言和实验证据,综述了近年来Rh(Z=45),Pd(Z=46),Ag(Z=47),Cd(Z=48)(质子数Z位于Ru,Z=44之上)及Zr(Z=40),Nb(Z=41),Mo(Z=42),Tc(Z=43)(质子数Z位于Ru,Z=44之下)的A～(100～126)丰中子同位素中关于三轴形变的形状变迁和形状共存系统性研究的重要进展。252Cf自发裂变瞬发γ射线γ-γ-γ三重符合、特别是新建立的γ-γ-γ-γ四重符合数据的系统观测和研究,在Ru,Pd,Cd和Nb丰中子同位素中显著扩展或首次观测到了一系列能带,为这个核区原子核形状的研究提供了新的、重要的实验数据。联系此前报道的有关进展,使用PES,TRS,PSM,CCCSM和SCTAC理论模型计算拟合新的实验数据,在该核区沿同中素和同位素链,并随自旋和激发能变化各自由度,跟踪原子核形状渐进变化,获得了新的系统性研究成果,显著扩展和深化了人们对原子核形状变迁和形状共存的认知。对于Ru及其上的Rh(Z=45),Pd(Z=46),Ag(Z=47)和Cd(Z=48)丰中子同位素的研究表明:Rh丰中子核具有比最大值稍小的三轴形变,γ=-28°,并在103–106Rh同位素链上鉴别出了手征对称破缺;在三轴形变核112Ru和114Pd(N=68)中发现了三轴原子核的摆动运动,该摆动运动也可能在114Ru(N=70)中存在;观察到了从具有最大三轴形变的110,112Ru中手征破缺到稍小三轴形变的112,114,116Pd中扰动的手征破缺的过渡;在较软的Ag核中观察到了丰富的谱学结构,在104,105Ag中鉴别出了可能的手征对称破缺,在较重的115,117Ag中提出了趋于三轴形变的γ软度;具有小形变的Cd核的能级结构被解释为准粒子耦合、准转动和软三轴形变;最近的库伦激发的研究提供了Z=50,N=82满壳附近122,124,126Cd核中出现核集体性的实验和理论证据;上述研究成果展现出从Ru中的最大三轴形变(γ=-30°,三轴形变极小增益为0.67 Me V),经具有大三轴形变的Rh核(γ=-28°),到Pd核中的稍小、但稳定于中等自旋到高自旋区的三轴形变(γ～-41°,三轴形变极小增益为0.32 Me V),再经Ag核中的γ软度,最后到具有很小形变、但仍出现集体性质、包括软三轴形变的Cd核的过渡。对于Pd核转动带交叉系统性的研究揭示了其第一带交叉(νh11/2)2中子转动顺排的上行γ驱动,和第二带交叉(πg9/2)2质子转动顺排的下行γ驱动效应,成功地解释了114Pd中的三轴摆动运动,并给出了110-118Pd同位素链中理论早已预言、而比早期理论预言更为完整准确的形状渐进变迁和形状共存的图像。根据该核区的系统研究,发现最大三轴形变出现在112Ru,而在相邻的偶Z(Pd)同位素链,三轴形变极小的中心在114Pd,两者均为N=68。上述系统性研究沿相邻的Ru和Pd偶Z同位素链,在N=68同中素中鉴别出最大三轴形变,均比理论预言的108Ru和110Pd多4个中子。在Z值位于Ru(Z=44)之下的Zr(Z=40),Nb(Z=41),Mo(Z=42)and Tc(Z=43)丰中子同位素中,Y和Zr核具有很强的轴对称四极形变,而在较重的Zr同位素中出现了γ自由度;较重的Nb核(A=104～106)基态具有中等程度的软三轴形变和强四极形变,随着自旋和激发能的增加,过渡到接近于轴对称的强四极形变;而较轻的Nb核(A 103)基态均接近轴对称形状;在Nb同位素链上基态由球形到强四极形变的形状突变发生在100Nb(N=59),在100–106Nb同位素链中基态的软三轴形变随中子数增加而增加;在Nb核中还观察到关于软三轴形变的形状共存;Mo核具有大的三轴形变,观察到了γ振动和手征对称破缺;Tc核具有比最大值稍小的三轴形变,γ=-26°,并观察到了手征对称破缺。质子数Z从41到48的A～(100～126)丰中子同位素,特别是Pd和Nb同位素,呈现出关于三轴形变的过渡特征。
基金Supported by National Key Basic Research Program of China(2013CB83440)''National Natural Science Foundation of China(11235001,11320101004)
文摘Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in 72Kr to prolate in 74,76Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0＋ states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes （except the ground state of 72Kr）, the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed.
基金Supported by National Key Basic Research Program of China(2013CB834402)National Natural Science Foundation of China(11235001,11320101004 and 11575007)
文摘Configuration-constrained potential-energy-surface calculations have been performed to investigate the K isomerism in the proton-rich A～ 80 mass region. An abundance of high-K states are predicted. These high-K states arise from two and four-quasi-particle excitations, with K^π= 8^＋ and K^π= 16^＋, respectively. Their excitation energies are comparatively low, making them good candidates for long-lived isomers. Since most nuclei under study are prolate spheroids in their ground states, the oblate shapes of the predicted high-K states may indicate a combination of K isomerism and shape isomerism.
