中重核中单粒子与集体运动的竞争效应(英文)

从原子核的电四极跃迁强度B（E2）中可以提取出原子核集体性和单粒子性质竞争的重要信息,其中一个重要的观测量是B（E2;4₁+ →2₁+）/B（E2;2₁+ →g.s.）的比值（B_4/2）。B_4/2一般要大于1,而且对于原子核转动和振动,我们应有B_4/2=1.4和2.0,但球形半满壳核一般会有不一样的性质。这些核的性质主要受对关联效应影响。介绍了几种超出我们一般认识的奇特衰变性质。Te同位素的基态带有鲜明的振动特性,但114Te的E2跃迁性质却更符合转动性。这些性质可以通过大规模壳模型计算来描述。对于填充j=9/2轨道的半满壳核,它们的4+和6+显示出很强的辛若数部分守恒性质。这种奇特的部分守恒可以被解析证明。而且我们的计算表明辛若数部分守恒对相关的E2跃迁影响很大。对于N=90附近具有量子相变行为的核素,其B_4/2也会也表现出相似的奇异特性。The E2 transition strength, B(E2), gives particularly precise information on the competition between the collective and single-particle degree of freedom. An important observable to study the development of collectivity is the B(E2; 4₁+ →2₁+)/B(E2; 2₁+ →g.s.) (B_4/2). The B_4/2 ratio is usually greater than unity. These values are 1.4 and 2.0 for an ideal rotor and a vibrator, respectively. Whereas the seniority scheme usually leads to different behaviours. In this contribution I will show examples that contrast with our standard understanding. The yrast spectra of Te isotopes show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behaviour, which cannot be reproduced by collective models. Large-scale shell model calculations reproduce well the equally-spaced spectra of those isotopes as well as the constant behaviour of the B(E2) values in 114Te. For nuclei involving protons or neutrons in j=9/2 orbitals, the partial conservation of seniority can lead to dramatic changes to the E2 decay pattern that have never been seen before. The B_4/2 ratios in quantum phase transitional nuclei around N=90 also show a similar exotic feature.     

关于~(93)Mo中21/2~+晕阱的来源（英文）

本研究通过壳模型计算研究了N=51的同中子素~(91)Zr、~(93)Mo和~(95)Ru中高自旋晕态21/2~+的同核异能态现象。计算发现,低角动量的p_(1/2)轨道上的质子是仅在~(93)Mo中存在21/2~+晕阱的主要原因。同时,本工作还研究了N=52的同中子素~(92)Zr、~(94)Mo和~(96)Ru中10_1~+-12_1~+能级结构的系统性,发现~(94)Mo中的10_1~+-12_1~+能级间隙相对最小,考虑到与~(93)Mo的17/2_1~+-21/2_1~+能级相似的组态,这一结果为~(93)Mo中出现21/2~+晕阱提供了补充性的论证。     

球形平均场加四极-四极和对力模型在单j壳内的量子相交叉行为(英文)

介绍了单j壳的球形平均场加几何四极-四极和标准对力模型的量子相交叉行为。在单j=15/2的壳内,计算了随模型控制参数变化的多个物理量如低激发能级、激发态间重叠积分、低激发态间的B（E2）比值和电四极矩比值。结果显示,在类转动到对激发相的演化中,多个物理量在交叉区存在非常明显的变化,如B（E2;4₁ → 2₁）/B（E2;2₁ → 0_g）,B（E2;4₂ → 2₁）/B（E2;2₁ → 0_g）等,并且这些变化在核子数达到半满壳时尤为显著。此外,尽管当j较小时,由几何四极-四极相互作用得到的低激发能级不满足转动谱规律,但当j值足够大时,这些低激发能级满足转动谱规律。The analysis of the quantum phase crossover behavior in the spherical shell model mean-field plus the geometric quadrupole-quadrupole (Q·Q) and standard pairing model within a single-j shell is reported. Several quantities, such as low-lying excitation energies, the overlaps of excited states, ratios of some B(E2) and electric quadrupole moments of some low-lying states as functions of the control parameter of the model in a j=15/2 shell are calculated. The results show that there are noticeable changes in the crossover region of the rotational-like to the pair-excitation phase transition, such as B(E2;4₁ → 2₁)/B(E2;2₁ → 0_g) and B(E2;4₂ → 2₁)/B(E2;2₁ → 0_g), especially in the half-filling case. Though the low-lying excitation energies generated from the geometric quadrupole-quadrupole interaction not satisfy the pattern of a rotational spectrum when j is small, these energies follow the pattern of a rotational spectrum when j is sufficiently large.     

丰中子锶同位素的投影壳模型研究

利用考虑跨壳激发的投影壳模型（PSM）方法,研究了质子数Z=38、中子数N=63和64大形变丰中子101,102Sr同位素的结构性质。主要计算了转动谱、转动惯量和电磁跃迁性质等（如B（E2）和g因子）,并与相应的实验数据进行系统比较和相关的理论预言。结果表明,PSM可以利用理论计算的能带图解释101,102Sr同位素的转动惯量、电磁跃迁随自旋的变化,分析晕带的结构。PSM理论可以很好地再现实验结果,说明PSM方法及其采用的有效相互作用可以外推研究丰中子核区101,102Sr同位素的原子核结构。对于101,102Sr同位素,核子开始填布质子g_9/2和中子h_11/2轨道,通过更为仔细地分析能带图中来自质子g_9/2和中子h_11/2轨道对各转动带的组态成分的贡献,清晰地表明丰中子核结构性质对不同核子填布的依赖。Recently, we have carried out systematically studies on the structural properties of proton number Z=38, neutron number N=63 and 64 neutron-rich isotopes 101,102Sr by using the projected shell model (PSM) with consideration of cross shell excitation. The rotation spectra, the moment of inertia and the electromagnetic transition properties (such as B(E2) and g-factor) are calculated and compared with the corresponding experimental data in this paper. Furthermore, more high spin states are predicted in the calculation and expected to be confirmed experimentally. The results show that the PSM can not only well analyze the structural properties of yrast bands in 101,102Sr but also interpret the variation of the moment of inertia, electromagnetic transition with spins in terms with the theoretical band diagram. The good agreement with the experimental data suggests that the PSM with the adopted effective interactions can be generalized to study the nuclear structure of 101,102Sr isotopes in neutron-rich mass region. For 101,102Sr isotopes, the nucleons begin to fill proton g_9/2 and neutron h_11/2 orbital, the dependence of nuclear structure and properties on the different orbital occupies is described by carefully analyzing the contribution from proton g_9/2 and neutron h_11/2 orbital to the configuration of rotational bands in band diagram.     

丰中子锰同位素的壳模型计算

利用球形壳模型和投影壳模型两种方法对Z≤28,N=40附近pf壳的丰中子核素的结构进行了一系列的研究。以丰中子的锰同位素为例讨论了对奇奇核58,60Mn的两种壳模型计算结果。结果显示,两种理论方法都很好地再现了58,60Mn实验上观测到的从低激发到高自旋态的能级。在对这两个同位素由中子g_9/2轨道闯入所产生的负宇称转动带进行描述时,两种理论计算也得到了一致的结果。通过对比,阐明了两种壳模型方法及其采用的有效相互作用在该丰中子核区的适用性,特别强调了中子g_9/2轨道的激发对于pf壳Z≤28丰中子核素结构的重要性。Recently,we have carried out a series of studies on the structures of pf shell neutron-rich nuclei around N=40 using the spherical shell model and the projected shell model respectively.As an example,these two types of shell model calculations for the neutron-rich odd-odd isotopes 58,60Mn are discussed in this paper.The results show that both the calculations reproduce the observed experimental energy levels from the lowexcitation states to the high-spin ones in 58,60Mn.Consistent results are also obtained by these two theoretical calculations when describing the negative-parity rotational band derived from the intruder neutron g_9/2 orbital in both isotopes.Through comparison,we show the applicability of these two shell model methods and the adopted effective interactions in the present neutron-rich mass region.The significance of the excitations from neutron g_9/2 orbital to the structures of the neutron-rich nuclei in pf shell with Z≤28 are especially emphasized in this paper.     

可能的原子核形状及硬度演化性质:基于能量面计算的系统分析(英文)

基于（β₂,γ,β₄）形变空间下对-形变自洽的原子核能量面计算方法,系统研究分析了50 < Z < 82区偶偶核的形状及硬度演化特征。计算的平衡形变与其它理论预言及存在的实验值进行了对比。从相应的形变势能曲线提取了与β₂及γ相关的硬度参数C_β,C_γ,这与实验观测到的低位β及γ振动带信息相符。还简要讨论了转动情况下的硬度演化,例如基于蜈蚣型E-GOS曲线,表明存在不可忽略的振动效应。Nuclear shape and stiffness evolutions in even-even nuclei with 50 < Z < 82 are systematically analyzed in terms of the pairing-deformation self-consistent nuclear-energy-surface calculation in (β₂,γ,β₄) deformation space. Calculated equilibrium deformations are presented and compared with other theoretical predictions and available experimental data. The stiffness parameters C_β and C_γ respectively related to quadrupole deformations β₂ and γ are determined from the deformation energy curves, which are consistent with the observed low-lying β and/or γ bands. The stiffness evolution under rotation along the yrast line is briefly discussed, e.g., on the basis of the centipidelike E-GOS curves, showing an unnegligible vibration effect.     

Er,Yb同位素链的基态形状(量子相)酷越研究(英文)

利用严格求解的Nilsson轴形变平均场加扩展对力模型,对Er和Yb同位素链基态形状（量子相）酷越进行了研究。通过该模型下能级比R_02+/21+、奇偶能差、信息熵的计算,成功地再现了155-163Er和157-165Yb同位素相关物理量的形状（量子相）酷越行为。通过分析这些量随着四极形变参数和总体对力强度的变化过程,显示了这种酷越行为主要是由于对力强度与四极形变之间的竞争导致的,该结果揭示了本模型下的基态形状（量子相）酷越行为的来源。Ground-state shape (phase) crossover in Er and Yb isotopes is manifested in the axially deformed Nilsson mean-field plus extended pairing model. The energy ratio R_02+/21+, the odd-even mass differences and the information entropy are calculated under the present model, reproduce the shape (phase) crossover behaviors of these quantities in 155-163Er and 157-165Yb isotopes. From the analysis of these quantities as functions of the quadrupole deformation parameter and the overall pairing interaction strength, it is shown that the crossover is mainly driven by the competition between the pairing interaction and the quadrupole deformation, which thus provides the origin of the shape (phase) crossover in the present model.     

铜原子单激发态3d104p 2P1/2的光电离(英文)

铜原子能级结构的理论计算具有非常大的挑战性。本文基于多组态Dirac-Hartree-Fock（MCDHF）方法和相对论组态相互作用（RCI）方法,通过三个大规模的关联模型计算了单激发态3d104p 2P_1/2、双激发态3d94s（3D）5s4D_3/2,1/2,3d94s（3D）5s 2D_3/2,3d94s（1D）5s 2D_3/2以及离子态3d10 1S₀能级和波函数。结果表明,铜原子能级结构对有限组态空间的选择极其敏感,双激发态3d94s（3D）5s 4D_3/2,1/2,3d94s（3D）5s 2D_3/2,3d94s（1D）5s 2D_3/2和离子态3d10 1S₀与单激发态之间的能量差相对于已有实验结果均存在大约-0.4 eV的偏差,而计算得到的共振电子能量与实验结果符合得较好。此外,根据辐射跃迁矩阵元和非辐射跃迁矩阵元计算了双激发态的Fano参数q,并基于Fano理论得到了铜单激发态3d104p 2P_1/2的总光电离截面,该理论考虑了直接光电离与光激发自电离之间的干涉效应,即共振3d94s（3D）5s 4D_3/2,1/2、3d94s（3D）5s 2D_3/2和3d94s（1D）5s 2D_3/2具有明显的非对称的Fano轮廓,表明光电离过程与光激发自电离过程之间的干涉对双激发态共振附近的光电离截面轮廓有着极其重要的影响。     

基于结团形成模型系统研究Z=82,N=126闭壳附近原子核的α衰变

基于结团形成模型（cluster-formation model,CFM）系统地研究了质子数Z=82,中子数N=126闭壳附近的α衰变母核的α衰变预形成因子P_α。计算结果表明:基于结团形成模型计算得到的P_α线性地依赖于价质子（空穴）N_p和价中子（空穴）N_n的乘积。这与前期工作[SUN X D,et al.Phys Rev C,2016, 94 （2）:024338;DENG J G,et al.Phys Rev C,2017, 96 （2）:024318]得到的结论是一致的,其中,P_α是唯象的且模型依赖的,从α衰变半衰期的理论值和实验值的比值中提取。结合前期工作可以得到这样的结论:对于Z=82,N=126闭壳附近的α衰变母核,其P_α与N_pN_n呈线性关系,且价质子-价中子相互作用在α结团预形成中起了很重要的作用。In the present work, the α decay preformation factors P_α are systematically studied within the cluster-formation model (CFM) for nuclei around Z=82, N=126 closed shells. The calculations show that the P_α calculated by CFM is linearly dependent on the product of valance protons (holes) and valance neutrons (holes) N_p N_n. It is consistent with our previous works[SUN X D, et al. Phys Rev C, 2016, 94 (2):024338; DENG J G, et al. Phys Rev C, 2017, 96 (2):024318], which P_α are model-dependent and extracted from the ratios of calculated α decay half-lives to experimental data. Combining with our previous works, we confirm that the P_α is linearly dependent on the N_pN_n for nuclei around Z=82, N=126 shell closures. In addition, the valance proton-neutron interaction plays a key role in the α preformation.     

192Tl高自旋态能级结构研究

通过熔合蒸发反应181Ta（16O,5n）192Tl,在入射束流为97 MeV能量下,布居192Tl的高自旋态,更新了192Tl的能级纲图。共增加8条新能级,尝试性地指定了能级自旋,将负宇称晕带的能级推高到23-?。讨论了192Tl与相邻同位素奇奇核194,196,198Tl负宇称晕带的旋称劈裂与反转现象,发现随着中子数增加,196,198Tl在高自旋处出现了旋称反转,其原因可能是由于中子质子相互作用与科里奥利力相互竞争所致。High spin states of 192Tl were populated by the 181Ta(16O, 5n)192Tl heavy ion fusion evaporation reaction at 97 MeV beam energy. A new level scheme with 8 new levels was constructed and the level spins were tentatively assigned. The negative yrast band was extended up to 23-?. Systematics of signature of inversion were also discussed for the negative yrast band of odd-odd Tl istopes. Signature inversion has been found in 196,198Tl with neutron number increasing in these four Tl isotopes, and it is explained by the competition between the strength of n-p interaction and Coriolis force.     

Inhibited transitions and isomeric states in the N = 50 isotones

Measured E2 transition rates in the N = 50 isotones (⁹⁰Zr–⁹⁴Ru) are satisfactorily reproduced by a shell model 0699 0 with proton configurations (p_1/2g_9/2)ⁿ. The inhibited 8⁺→6⁺ E2 transition in ⁹⁴Ru and its connection with seniority mixing is discussed. Isomeric states are predicted in ⁹¹Nb and ⁹³Tc. 0699     

Proton–neutron structure of the N=52 nucleus Zr

Following the successful identification of mixed-symmetric one- and two-phonon states in the N=52 nuclei ⁹⁴Mo and ⁹⁶Ru, we have performed a photon scattering experiment on the N=52 isotone ⁹²Zr. Experimental data and shell model calculations show that both, single particle and collective degrees of freedom are present in the low-lying levels of ⁹²Zr. The second excited quadrupole state shows the signatures of the one-phonon mixed-symmetric 2⁺ state, while calculations and data indicate an almost pure neutron configuration for the 2⁺₁ state, in contradiction with the F-spin symmetric limit. Furthermore, two strong dipole excitations, which are candidates for the two-phonon quadrupole–octupole coupled E1 excitation and for the mixed-symmetric 1⁺ two-phonon state, were observed.     

Decay of Ru, Zr and Nb

The decay of ⁹⁷Ru, ⁹⁷zr and ⁹⁷Nb to levels in ⁹⁷Tc, ⁹⁷Nb and ⁹⁷Mo has been studied with Ge(Li), NaI(Tl), plastic scintillation, and Si (Li) detectors in singles and coincidence experiments. Level schemes were constructed with states in ⁹⁷Te at 96.5, 215.2, 324.4, (560), 785.5, 856 and 971 keV; in ⁹⁷Nb at 743.5, 1148.6, 1251.4, 1276.6, 1549.2, 1751.2, 1764.0, 1852.0, 2106.9 and 2247 keV; and in ⁹⁷Mo at 656.0, 1022.0, 1274.5 and 1514 keV. From β-endpoint energies, disintegration energies of ⁹⁷Zr and ⁹⁷Nb were determined to be 2580 ± 50 keV and 1830 ± 50 keV, respectively. Decay scheme considerations and an upper limit to the β⁺/ec ratio established the disintegration energy of ⁹⁷Ru to be about 1100 keV. Neither the effective-interaction method nor the pairing-correlation model accounts for the experimentally determined levels in mass-97 nuclei.     

Na_2~+离子较低电子态势能曲线和光谱常数的理论研究

通过多组态相互作用方法,结合原子有效芯势与极化势,利用非收缩的高斯基函数,计算了Na_2~+分子对应最低9个解离限的36个电子态的势能曲线.基于计算获得的束缚态势能曲线,拟合给出了相应的光谱常数,并与已有的实验和理论结果进行了比较.同时,给出了部分电子态的振动-转动能级和一些同类态避免交叉点的信息.计算获得的光谱信息对冷原子分子光谱与动力学的研究具有参考价值.     

AlH~+离子5个Λ-S态和10个?态的光谱性质以及激光冷却的理论研究

利用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法结合相关一致基组aug-ccpV6Z计算了AlH~+离子前两个离解极限对应的5个Λ-S态和10个?态的势能曲线.为了提高势能曲线的可靠性和精确性,计算中考虑了自旋轨道耦合效应、芯电子价电子相关和标量相对论修正以及将势能外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的4个Λ-S态和8个?态的光谱常数和振动能级,与已有的实验结果符合.计算了2(1/2)→X~2Σ_(1/2)~+和A~2Π_(3/2)→X~2Σ_(1/2)~+跃迁的跃迁偶极距.利用计算的精确的势能曲线和跃迁偶极矩,获得了2(1/2)~(第一势阱)(υ′=0, 1)→X~2Σ_(1/2)~+(υ′′)和A~2Π_(3/2)(υ′=0, 1)→X~2Σ_(1/2)~+(υ′′)跃迁的高度对角化分布的Franck-Condon因子(f_(00)和f_(11))和大的振动分支比;预测了2(1/2)~(第一势阱)(υ′=0, 1)和A~2Π_(3/2)(υ′=0, 1)态短的自发辐射寿命和窄的辐射宽度,这适合于AlH~+离子的快速激光致冷.所需的3束激光冷却波长都在紫外区域.这些结果表明了激光冷却AlH~+离子的可行性.此外,评估了自旋轨道耦合效应对光谱常数、振动能级和激光冷却AlH~+离子的影响.     

95Zr(n,γ)96Zr的间接测量

95Zr（n,γ）96Zr是稳定燃烧的恒星中合成96Zr的唯一途径,对研究恒星演化和重元素合成具有重要的意义。由于95Zr半衰期为64 d,直接测量95Zr（n,γ）96Zr截面极为困难,因此,本工作采用替代比率法间接测量95Zr（n,γ）96Zr截面。本工作测量了94Zr（18O,16Oγ）96Zr和90Zr（18O,16Oγ）92Zr反应,得到了复合核96Zr*和90Zr*衰变到γ道的几率比,并利用截面已知的91Zr（n,γ）92Zr截面乘以实验所测比率,得到了E_n=0~8 MeV能区的95Zr（n,γ）96Zr中子俘获截面。95Zr(n, γ)96Zr cross section is important for the study of stellar evolution and heavy elements nucleosynthesis because the reaction is the only way to produce the 96Zr in Asymptotic giant branch stars. The direct measurement of 95Zr(n, γ)96Zr is very difficult due to the short half-life of 95Zr, 64 days. The surrogate ratio method was carried out to measure 95Zr(n, γ)96Zr cross sections. We measured the 94Zr(18O, 16Oγ)96Zr and 90Zr(18O, 16Oγ)92Zr reactions and obtained the γ-decay probability ratio of compound nuclei 96Zr* and 92Zr*. The 95Zr(n, γ)96Zr cross section is determined by the obtained ratio multiplying the known 91Zr(n, γ)92Zr cross section at E_n=0~8 MeV.     

High-spin study of Xe

High-spin states have been populated in ₅₄¹¹⁹Xe via the ⁹⁶Mo(²⁷Al,p3n) reaction at 133 MeV, using the γ-ray spectrometer to record triple γ-ray coincidences. The known level scheme has been significantly extended and several band crossings identified. In particular, the νh_11/2 yrast band has been extended to I^π = (83/2⁻) and shows features which are consistent with those of smooth band termination at high spin. Theoretical results for ¹¹⁹Xe at high spin are discussed within the framework of cranked Nilsson-Strutinsky calculations, together with results for ¹¹⁷Xe.     

LiNbO3和LiTaO3晶体Er3+/Yb3+掺杂水热外延层室温吸收光谱分析

本文引入与浓度和厚度有关的k_NL待定参数, 在J-O理论基础上, 对Er³⁺/Yb³⁺掺杂的LiNbO₃和LiTaO₃单晶衬底上 的多晶水热外延样品进行了基于吸收光谱的拟合计算. LiNbO₃:Ω₂=2.34× 10^-20 cm², Ω₄=0.77× 10^-20 cm², Ω₆=0.31×10^-20 cm², k_NL=4.32× 10^-2 mol·m^-2. LiTaO₃:Ω₂=1.68×10^-20 cm², Ω₄=0.84×10^-20 cm², Ω₆=0.45×10^-20 cm², k_NL=9.17×10^-3 mol· m^-2. 该方法可尝试推广到粉体或胶体等难以直接获得浓度和厚度数据的体系. 经上转换发光测试及光谱参数计分析认为Er³⁺/Yb³⁺离子的掺杂浓度比为1:1的情况下, 样品呈现绿色上转换发光光谱; 可尝试以降低基质声子能量的方法提高⁴I_13/2能级 对²H_11/2和⁴S_3/2能级的量子剪裁效率.     

Reanalysis of the Z_c(4020), Z_c(4025), Z(4050) and Z(4250) as Tetraquark States with QCD Sum Rules

In this article, we calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the C γμ- Cγνtype scalar, axial-vector and tensor tetraquark states in details with the QCD sum rules. In calculations, we use the formula μ = (M 2X/ Y /Z-(2Mc)2)~(1/2) to determine the energy scales of the QCD spectral densities. The predictions MJ =2=(4.02+0.09-0.09) GeV, MJ =1=(4.02+0.07-0.08) GeV favor assigning the Zc(4020) and Zc(4025) as the JP C= 1+-or 2++diquark-antidiquark type tetraquark states, while the prediction M++J =0=(3.85+0.15-0.09) GeV disfavors assigning the Z(4050) and Z(4250) as the JP C= 0diquark-antidiquark type tetraquark states. Furthermore, we discuss the strong decays of the 0++, 1+-, 2++diquark-antidiquark type tetraquark states in details.     

Microscopic Description of g Factors and M1 Properties in Platinum Isotopes

Starting from the shell model configurations, valence nucleon effective interactions and fermion M1 transition current density operator, the counterparts in the proton-neutron interacting boson model (sdIBM-2) of the fermion Hamiltonian and M1 transition current density operator are derived microscopically with the help of Dyson expansion technique. The boson g factors are abstracted from the boson M1 transition current density operator. Spectra, g factors of 2₁⁺, 2₂⁺, 4₁⁺ states and M1 matrix elements between 2₂⁺ and 2₁⁺ are calculated for the even ^192-198Pt isotopes in the sdIBM-2. The theoretical results fit experimental data quite well.