Structure Evolution in the Even-Even 124-134Xe with IBM2

We have investigated the structure evolution of the ^124-134Xe isotopic chain in the framework of the proton-neutron interacting model IBM2. The positive parity spectra of the ground state, quasi-β and quasi-γ bands are reproduced well. The staggering in ^124-130Xe are almost completely removed and the γ band agree well with the experiment data, even for the high-spin quasi-γ states. The key quantities of the collective structure evolution, including level energies, the B(E2) transition branching ratios, and the M1 excitations to 1₁⁺ mixer-symmetry states are analyzed by comparing with the experimental data. The parameters for representation of the O_πν(6) and SU_πν^*(3) features in isotopes are examined. Both experimental data and theoretical results show that the shape phase transition of ^124-134Xe isotopic chain is from the SU_πν^*(3) (triaxial rotation) to the U_πν(5) (vibration motion) with a considerable constituent of the O_πν(6) symmetry (γ-unstable rotation), where the shape phase transition rapidly takes place between the neutron number N = 76 and N = 78.     

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     

Projectile coulomb excitation of Ne and Ne

The static quadrupole moments of the first excited J^π = 2⁺ states in ²⁰Ne and ²²Ne and the reduced electric quadrupole transition probabilities of these states to the ground states were measured via projectile Coulomb excitation. The quadrupole moments were deduced from the shapes of γ-ray angular distributions. The results are: Q(²⁰Ne, 2⁺) = −0.20±0.05 b and Q(²²Ne, 2⁺) = −0.11±0.05 b. The transition strengths were deduced from yield measurements and by comparison with the yields of target γ-rays. The results are: B(E2; 0⁺ → 2⁺, ²⁰Ne) = 0.037±0.003 e² · b² and B(E2; 0⁺ → 2⁺, ²²Ne) = 0.025±0.002 e²· b². The results for the transition strengths are consistent with the results of accurate timing methods and resolve discrepancies between previous experiments. The results for the quadrupole moments are consistent with earlier measurements, although the mean values we obtain are slightly lower. The experimental measurements are compared with theoretical predictions and a detailed discussion is given of corrections to this type of reorientation experiment.     

Backbending and E2 reduction in Ba

The E2 transition strengths of yrast states in ¹²⁶Ba are measured. A reduction of a factor of three is observed for the 10⁺→8⁺ and 8⁺→6⁺ transitions. This seems to indicate that the E2 reductions and the backbending pattern in this nucleus are uncorrelated.     

An Approach of the Nuclear Transition Charge Density Calculation in the Microscopic sdIBM-2

An approach to calculate the nuclear transition charge density (TCD) within the framework of the microscopic sdIBM-2 is presented and applied to the ¹⁹⁰Os first. It was found that the TCD as well as the spectrum and some reduced E2 transition matrix elements in ¹⁹⁰Os can be reproduced quite satisfactorily on the same microscopic footing.     

A microscopic study of the octupole degree of freedom at high angular momentum

A microscopic parity and number projected calculation after the variation was used to describe the rotational bands of the octupole deformed nuclei ¹⁴⁴Ba, ¹⁴⁶Ce and ²²⁴Ra. The states obtained in a cranked Hartree-Fock-Bogoliubov approach are taken as intrinsic states for the parity and number projection. Dipole moments, deformation parameters, B(E1), B(E2) and B(E3) transition probabilities along the band are obtained and compared with the available experimental data. The calculations have been done with the finite range density dependent Gogny force.     

In-band M1 and E2 transition rates and collective structures in Ba

Subpicosecond mean lifetimes of eight excited states in ¹²⁸Ba populated via the ⁹⁶Zr(³⁶S,4n) reaction were measured by the Doppler-shift attenuation (DSA) technique using a line-shape analysis. The differential decay-curve method (DDCM) was applied for the lifetime determination. The B(E2) values in the yrast band indicate that the first band-crossing is with a proton S-band. The configuration πh_11/2d_5/2 of the negative-parity semi-decoupled bands is confirmed by the measured B(E2, I → I − 2) and B(M1, I → I − 1) transition strengths. The higher-lying “dipole” band in ¹²⁸Ba can be described as a high-K four-quasiparticle band built on the prolate configuration (πh_11/2d_5/2) (νh_11/2g_7/2).     

The Structure of the Neutron-Rich Nd Isotopes in the IBM

The spectra and E2 transition properties of ^146-156Nd isotopes are studied in the interacting boson model in the light of new experimental data. It is found that ^146-150Nd are in the transition from the vibrational limit to the rotational limit. From ¹⁵²Nd onward, the isotopes are nearly perfect rotors. Possible deformation saturation is discussed in the interacting boson model.     

Low-lying electronic states of CuN calculated by MRCI method

The high accuracy ab initio calculation method of multi-reference configuration interaction(MRCI) is used to compute the low-lying eight electronic states of CuN.The potential energy curves(PECs) of the X~3∑~-,1~3Π,2~3∑~-,1~3△,1~1△,1~1∑~-,1~1Π,and ~5∑~- in a range of R=0.1 nm-0.5 nm are obtained and they are goodly asymptotes to the Cu(~2S_g) + N(~4S_u) and Cu(~2S_g)+N(~2D_u) dissociation limits.All the possible vibrational levels,rotational constants,and spectral constants for the six bound states of X~3∑~-,1~3Π,2~3∑~-,1~1△,1~1∑~-,and 1~1 Π are obtained by solving the radial Schrdinger equation of nuclear motion with the Le Roy provided Level 8.0 program.Also the transition dipole moments from the ground state X~3∑~- to the excited states 1~3Π and 2~3∑~- are calculated and the result indicates that the 2~3∑-X~3∑ transition has a much higher transition dipole moment than the 1~3Π-X~3∑~- transition even though the l~3Π state is much lower in energy than the 2~3∑~- state.     

Shape Transition and Triaxial Interaction Effect in the Structure of 152-166Dy Isotopes

The positive parity states in even-even ^152-166Dy are studied systematically in the framework of the interacting boson model (IBM). A cubic term, L=3, has been added to the Hamiltonian in order to produce the effect of triaxiality on the energy spectrum. The potential energy surfaces as a function of β and γ deformation parameters, for all isotopes have been produced. Energy levels and reduced electric quadrupole transition probabilities are calculated in framework of IBM with Cubic term (IBMC). All results are compared with available experimental data. It is found that these isotopes can be described by a schematic Hamiltonian in transition from U(5) (vibration) to SU(3) (rotation) dynamic symmetry.     

Pion-Rotational Nucleus Scattering and the Interacting Boson Model

A procedure of combining the medium energy scattering theory in the eikonal approximation with the interacting boson model (IBM) is proposed to study the pion-rotational nucleus scattering. The channel coupling effects in the excitation of nuclear collective state with π^- and π⁺ elastic and inelastic scattering are analyzed. The calculated cross sections for the excitation of 2₁⁺ state of ¹⁵²Sm agmree with the experimental data quite well.     

Pair Excitations in Even-Even Nuclei

A charge exchange term is added to the n-p effective interaction in treating eveneven nuclei with shape coexistence. The energy spectra and some of the E2 transition rates are calculated for ^112,114Cd, ^114,116Sn and ^118,120Te nuclei. The inclusion of this new term helps to improve an agreement with experimental data.     

Ground-State Bands of Fm and No Isotopes in Cluster Model

We investigate the ground-state rotational bands of nuclei with Z 〉 100 using cluster model proposed by Buck et al. [Phys. Rev. Left. 94 （2005） 202501]. The core-duster decomposition of each nucleus is determined by the corresponding electric quadrupole transition strength B（E2 ： 2^＋ → 0^＋）. The theoretical spectra of fermium and nobelium isotopes are compared with available experimental data. Good agreement between model and data is obtained.     

Nb XIII离子3d94s2, 3d94s4p, 3d94p2 组态能级结构与跃迁的理论研究

用准相对论Hartree-Fock方法对Nb XIII离子二电子激发组态3d⁹4s², 3d⁹4s4p, 3d⁹4p² 的能级结构做了全面系统的理论计算研究.在对已有研究结果分析的基础上, 运用最小二乘方法对径向积分参数进行了优化计算, 得到了与这些组态有关的电偶极允许跃迁的谱线波长和跃迁概率.计算结果与最新的实验值做了对比分析, 表明本文计算结果是准确的. 研究发现, 波长40.92 nm的谱线, 属于3d⁹4s(¹D)4p²F_7/2–3d⁹ (²D)4s^{2 2}D_5/2 的跃迁谱线, 而不属于3d⁹4s (¹D)4p⁴D_7/2–3d⁹(²D)4s^{2 2}D_5/2 的跃迁谱线, 即上谱项能级为²F_7/2, 而不是⁴D_7/2. 关键词： Nb XIII离子 二电子激发组态 谱线波长 跃迁概率     

Potential energy curves,transition dipole moments,and radiative lifetimes of KBe molecule

An ab initio calculations on the ground and low-lying excited states(X~2Σ+, 2~2Σ+, 3~2Σ+, 1~4Π, 2~4Π, 1~4Σ~+, 2~4Σ~+,and 3~4Σ~+) of KBe molecule have been performed using multireference configuration interaction(MRCI) plus Davidson corrections(MRCI+Q) approach with all electron basis set aug-cc-p CV5Z-DK for Be and def2-AQZVPP-JKFI for K.The 3~2Σ+, 1~4Π, 2~4Π, 1~4Σ~+, 2~4Σ~+, and 3~4Σ~+states are investigated for the first time. Inner shell electron correlations are computed on the potential energy curves(PECs) calculations. The spectroscopic and molecular parameters are also predicted. In addition, The transition properties including transition dipole moment, Franck–Condon factors qv'v', Einstein coefficients Av'v', and the radiative lifetimes τυ for the 2~2Σ~+–X~2Σ~+, 3~2Σ~+–X~2Σ~+, and 2~4Π–1~4Π transitions are predicted at the same time.     

YNbO4：Tm3+/Yb3+上转换发光特性研究

按照50Nb₂O₅-（46-x）Y₂O₃-4Yb₂O₃-xTm₂O₃（x=0.1,0.2,0.5,1,2）的配比方式,采用高温固相法制备出了掺杂Tm³⁺/Yb³⁺的YNbO₄晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm³⁺离子的¹G₄→³H₆、¹G₄→³F₄、³F₃→³H₆能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω_t（t=2,4,6）,进而得出理论振子强度及实验振子强度,二者均方根偏差δ_rms=1.299×10^-7。计算了Tm³⁺离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论：（1）³F₄能级寿命较长,适合作为上转换中间能级;（2）³H₅能级寿命较长,且³H₅→³H₆跃迁分支比（96.46%）接近100%,可用于产生1 216 nm激光。     

Effects of relativity and “atomic structure” in the KLL Auger spectrum of Sr generated in the EC-decay of Y

The KLL Auger electron spectrum of ⁸⁸Sr generated in the EC-decay of ⁸⁸Y has been analyzed at the instrumental resolution of 11 eV using a combined electrostatic spectrometer. Energies and relative intensities of the all nine transitions were determined and compared with theoretical predictions. Our value of 12067.3(12) eV measured for the absolute energy of the dominant KL₂L₃(¹D₂) transition was found to be higher by 7.4 eV (i.e., more than 3σ) than that one obtained in a measurement with external excitation. The discrepancy indicates substantial influence of the “atomic structure effect” on absolute transition energies in our experiment. Very good agreement of the measured 0.14(3) and predicted 0.12 values for the KL₁L₂(³P₀/¹P₁) Auger transition intensity ratio clearly proved the predicted strong influence of the relativistic effects on the KL₁L₂(³P₀) transition rate even at Z = 38.     

Determination of relative intensities of M internal conversion lines in pure E2 transitions

Accurate measurements have been performed on the relative intensities of the M internal conversion lines of three pure E2 transitions in nuclei in the rare-earth region. The results are compared with theoretical values obtained from the calculations by Bhalla and by Hager and Seltzer. Discrepancies of about 6% between experiment and theory are reported for the M_I/M_II and M_I/M_III ratios of the 80.57 keV transition in ¹⁶⁶Er. The M_II/M_III ratios of the 84.26 keV transition in ¹⁷⁰Yb and of the 100.09 keV transition in ¹⁸²W are significantly lower than predicted by theory.     

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.