^140-262Gd核的低能谱和电磁跃迁的相互作用玻色子模型

采用相互作用玻色子模型研究了^140-262Gd偶偶核的低能谱和电磁跃迁，应用一个U（5）→SU（3）的简化哈密顿量很好地描述它们的低能谱和电磁跃迁过渡．结果表明^140-262Gd同位素核基本上属于U（5）→SU（3）的过渡核．     

164—182Hf核的低能谱和电磁跃迁的相互作用玻色子模型

采用相互作用玻色子模型研究了^164—182Hf偶偶核的低能谱和电磁跃迁, 应用一个U(5)→SU(3)简化哈密顿量很好的描述它们的低能谱和电磁跃迁过渡. 结果表明^164—182Hf同位素核基本上属于U(5)→SU(3)的过渡核.     

142-164Dy核的低能谱和电磁跃迁的相互作用玻色子模型

采用IBM模型研究了^142-164Dy核的低能正宇称态的能谱和电磁跃迁。应用U(5)→SU(3)的简化哈密顿量较好地描述了它们的能谱和电磁跃迁。研究结果表明，该核基本属于U(5)→SU(3)的过渡核Spectra and E2 transition rates for the even even 142-164Dy isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian capable of describing their spectra and transition is used. It is found that the even even 142-164Dy isotopes are in the transition from U(5)to SU(3) dynamical symmetry.     

128—150Ce偶偶核的低能谱和电磁跃迁的相互作用玻色子模型

采用相互作用玻色子模型研究了^128—150Ce同位素核的低能正宇称态的能谱和电磁跃迁.应用简单的哈密顿量很好的描述它们的能谱和E2跃过.研究表明,这些偶偶Ce核是属于U(5)到SU(3)过渡核,而¹⁴⁶Ce以后的核基本是完全的转动核.     

原子核形状演变的又一个特征指标E0跃迁及对102—110Pd偶偶核的应用

利用相互作用玻色子模型分别在U(5)—SU(3)和U(5)—O(6)描述下研究了^102—110Pd偶偶核的电单极跃迁.研究表明,这些偶偶Pd核能够用U(5)—SU(3)更好地描述.     

A≈180质量区偶偶核形状相变研究

采用E-GOS方法对质子数在Z=72-78区的偶偶原子核170-184 Hf,170-184W,170-192Os和176-192Pt的集体运动模式和形状相变进行了研究.结果表明,170-184 Hf和170-184 W同位素核的低自旋态趋于SU(3)极限,176-192Pt和170-174Os同位素核是O(6)→U(5)的过渡核,并且基本上都存在角动量驱动的形状相变.     

重偶偶核的α结团现象与集体激发的统一描述

本文建立了统一描述重偶偶核的四极集体运动、α结团和八极振动的代数模型U(6)×U(11), 给出了该模型的三种动力学对称性: SU(5)、SU(3)和SO(6). 计算了SU(5)极限下的能谱, 并与²¹⁸Ra核的实验数据进行了比较.     

62-76Zn核的低能谱和电磁跃迁的相互作用玻色子模型(英文)

采用相互作用玻色子模型研究了62—76Zn核的低能正宇称态的能谱和电磁跃迁.应用一个简单的哈密顿量能够较好地描述它们的能谱和电四极跃迁.研究表明,62—76Zn同位素核基本上属于U(5)到O(6)的过渡核.Spectra and E2 transition rates for the even even 62-76Zn isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian capable of describing their spectra and transition is used. It is found that the even even 62-76Zn isotopes are in the transition from U(5) to O(6) dynamical symmetry.     

s-d-g模型中的四极算符与形变核能谱

本文在U(15)框架内讨论了偏离SU(3)极限的形变偶偶核能谱结构的变化趋势, 表明能谱结构主要由g玻色子贡献大小决定, 而且在偏离SU(3)极限处g玻色子的贡献减小.     

Gd同位素核混合对称态

本文应用中子-质子相互作用玻色子模型理论数值计算了¹⁵⁰Gd、¹⁵²Gd和¹⁵⁴Gd核混合对称态的能量和电磁跃迁几率.计算表明,¹⁵⁰Gd核最低能量的混合对称态是2⁺,而¹⁵²Gd和¹⁵⁴Gd则为1⁺,随着核子数的增加;B(M1,0⁺→1⁺)小变大,表现出U(5)极限向SU(3)极限的转移.另外Majorana相互作用对混合对称态能量和电磁跃迁几率的影响也作了讨论.     

Low-Lying Spectra and Electromagnetic Transition Rates in 140—162Gd in the Interacting Boson Model

Spectra and electromagnetic transition for the even-even ^140—162Gd isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian can be used to describe their spectra and transition. The results show that ^140—162Gd are in the transition from the vibrational limit to rotational limit.     

Temperature Dependence of the Magnetic Hyperfine Field at 140Ce on Gd Sites in GdAg Compound

Perturbed gamma–gamma angular correlation technique was used to measure the magnetic hyperfine field at Gd sites in the intermetallic compound GdAg using the ¹⁴⁰La→¹⁴⁰Ce nuclear probe. A major and well-defined magnetic interaction is observed at ¹⁴⁰Ce substituting Gd sites in GdAg below 130 K, corresponding to a ferromagnetic ordering of Gd moments. The temperature dependence of magnetic hyperfine field, however, shows a sharp deviation from an expected Brillouin-like behavior for temperatures below 75 K. This additional magnetic interaction is believed to result from the polarization of Ce spin moments induced by the magnetic field from Gd atoms.     

The magnetic and superconducting phase diagram of Gd-doped lanthanumsulfides

The system La_3-x( )_xS₄ [where ( ) denotes a vacancy] containing up to 25 at.% Gd is shown to be a model system in which magnetic interactions in metals can be studied. By measuring the temperature dependence of the low field a.c. susceptibility, the superconducting, spin-glass and ferromagnetic transitions can be determined as a function of the Gd concentration. The depression of the superconducting transition temperature mainly follows the theory of Abrikosov and Gor'kov, with a possibility for coexistence of superconductivity and spin-glass magnetic order near a critical concentration of 3 at.% Gd. The transition from spin-glass to ferromagnet is well-defined with the percolation limit for the long range ferromagnetic order at 14 at.% Gd.     

Making and breaking covalent bonds across the magnetic transition in the giant magnetocaloric material Gd5(Si2Ge2)

A temperature-dependent, single crystal x-ray diffraction study of the giant magnetocaloric material, Gd5(Si2Ge2), across its Curie temperature (276 K) reveals that the simultaneous orthorhombic to monoclinic transition occurs by a shear mechanism in which the (Si, Ge)-(Si,Ge) dimers that are richer in Ge increase their distances by 0.859(3) A and lead to twinning. The structural transition changes the electronic structure, and provides an atomic-level model for the change in magnetic behavior with temperature in the Gd5(SixGe1-x)(4).     

Role of Ge in bridging ferromagnetism in the giant magnetocaloric Gd5(Ge1-xSix)4 alloys

X-ray magnetic circular dichroism (XMCD) measurements and density functional theory (DFT) are used to study the electronic conduction states in Gd5(Ge(1-x)Si(x))4 materials through the first-order bond-breaking magnetostructural transition responsible for their giant magnetocaloric effect. Spin-dependent hybridization between Ge 4p and Gd 5d conduction states, which XMCD senses through the induced magnetic polarization in Ge ions, enables long-range Ruderman-Kittel-Kasuya-Yosida ferromagnetic interactions between Gd 4f moments in adjacent Gd slabs connected by Ge(Si) bonds. These interactions are strong below but weaken above the Ge(Si) bond-breaking transition that destroys 3D ferromagnetic order.     

Hyperfine interactions in intermetallic compounds between Gd and 3d transition metals

Measurements of hyperfine interactions at ¹⁵⁵Gd nuclei in metallic compounds between Gd and 3d transition metals and at ⁶¹Ni in GdNi compounds by Mössbauer spectroscopy are reported. The results are discussed in terms of various models proposed for the electronic structure of these compounds. The Gd isomer shifts with respect to metallic Gd are at variance with the model of a strong d electron transfer from rare earths to transition metal ions. From the observation of a linear relation between magnetic hyperfine fields at Gd and at Dy nuclei in corresponding compounds it is inferred that crystal-field induced variations of Dy moments are neglible and that the conduction electron polarization induced by 4f moments is directly related to that caused by 3d moments.     

Transition to a virtually incompressible oxide phase at a shock pressure of 120 GPa (1.2 Mbar): Gd3Ga5O12

Cubic, single-crystal, transparent Gd(3)Ga(5)O(12) has a density of 7.10 g/cm(3), a Hugoniot elastic limit of 30 GPa, and undergoes a continuous phase transition from 65 GPa to a quasi-incompressible (QI) phase at 120 GPa. Only diamond has a larger Hugoniot elastic limit. The QI phase of is more incompressible than diamond from 170 to 260 GPa. Electrical conductivity measurements indicate the QI phase has a band gap of 3.1 eV. Gd(3)Ga(5)O(12) can be used to obtain substantially higher pressures and lower temperatures in metallic fluid hydrogen than was achieved previously by shock reverberation between Al(2)O(3) disks.     

绿色荧光粉Gd2Ba3B3O12:Tb3+的发光性能研究

采用高温同相法制备了一系列Gd<,2>Ba<,3>B<,3>O<,12>:Tb<'3+>绿色荧光粉,借助X射线粉末衍射仪(XRD)、真空紫外光谱和荧光光谱仪(VUV-UV)对样品的物相、发光性能进行了表征.结果表明,Tb<'3+>作为发光中心全部进入到基质Gd<,2>Ba<,3>B<,3>O<,12>的品格中并占据Gd...