Field-induced order-disorder transition in antiferromagnetic BaCo(2)V(2)O(8) driven by a softening of spinon excitation

High field magnetization and ESR measurements on the quasi-one-dimensional (1D) antiferromagnet BaCo(2)V(2)O(8) have been performed in magnetic fields up to 50 T along the chain. The experimental results are explained well in terms of a 1D S=1/2 antiferromagnetic XXZ model in longitudinal fields. We show that the quantum phase transition from the Néel ordered phase to the spin liquid one in the model is responsible for a peculiar order to disorder transition in BaCo(2)V(2)O(8).     

基于扫描隧道显微镜的原子电子云结构

本文简要介绍了扫描隧道显微镜的基本工作原理，展示了一些扫描样品（石墨和铜）的电子云图，在简要介绍量子力学关于原子电子云结构基本理论的基础上，通过理论上的电子云结构与扫描结果的比较，在一定程度上验证了量子力学关于原子电子云结构理论的正确性．     

Investigation on improving characteristics of two-cell SBS system with CCl4/C2H5OH liquid mixture

In order to improve the performance of the two-cell stimulated Brillouin scattering （SBS） system, this paper proposes the methods of using mixtures, which require amplifier media to have small absorption rate, and generator media to have high optical breakdown threshold and Brillouin frequency shift equal to that of the amplification media. The characteristics of the two-cell SBS system are studied experimentally by using CCl4 as amplifier medium and CCl4, C2H5OH and CCl4/C2H5OH liquid mixture as generator medium pumped by Nd：YAG Q-switched laser. The obtained results show that liquid mixture in generator cell improves the power load ability, phase conjugation fidelity, energy reflectivity （ER） and ER stability.     

Structural and upconversion fluorescence properties of Er/Yb-codoped oxychloride lead-germanium-bismuth glass

Structural and infrared-to-visible upconversion fluorescence properties of Er³⁺/Yb³⁺-codoped oxychloride lead-germanium-bismuth glass have been studied. The Raman spectrum investigation indicates that PbCl₂ plays an important role in the formation of glass network, and has an important influence on the upconversion luminescence owing to lower phonon energy. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation.     

High-power continuous-wave operation of a diode-pumped laser at

The continuous-wave laser properties of an efficient diode-pumped Nd:GdVO₄ crystal operating at formed with a simple plane-concave cavity have been studied. With the incident pump power of 21 W, an output power of 6.9 W was obtained, giving an optical conversion efficiency of 32.8% and a slope efficiency of 35.3%. The laser characterization of two different Nd³⁺-doped concentration of Nd:GdVO₄ crystals were studied.     

飞秒强激光场中水分子的电离激发

本文运用含时密度泛函理论和分子动力学非绝热耦合的方法, 研究了水分子在不同极化方向的激光场中的电离和动力学行为. 计算结果表明, 对应相同的极化方向, 随着激光强度的增加, 水分子的电离增强; 对于相同强度的激光, 当激光极化方向沿水分子对称轴方向时, 水分子的电离最强, 当激光极化方向垂直水分子对称轴方向时, 水分子电离受到最大程度的抑制. 对水分子偶极矩的研究表明, 当分子处于线性响应区域时, x方向的激光只能激发起x方向的偶极振动而y方向的激光只能激发起y方向的偶极振动. 对水分子的键长和键角的研究表明, 在激光场中水分子的键长变长, 键角变大, 但变化幅度随着激光极化角的增大而减小. 此外, 研究还发现, 虽然在不同极化方向的激光脉冲的驱动下, 水分子OH键的振动频率与激光频率相当, 在脉冲关闭后, 振动频率减小, 但激光场的极化方向对水分子振动模式具有选择性. 关键词： 含时密度泛函理论 分子动力学 水分子 电离     

Stability of plane-wave Bose-Einstein condensation with spin-orbit coupling

In this paper, we prove analytically that the plane-wave Bose-Einstein condensates with spin-orbit coupling are stable in two dimensions at zero temperature. The SOC induced extra breaking of the O(2) symmetry of the ground state makes the goldstone modes more divergent in the infrared limit. But the depletions are still finite, which means the condensates are stable.     

D-T中子源n-γ密度测井规律的蒙特卡罗模拟

根据D-T反应中子的能谱和角分布数据,建立了中子源模型;根据石灰岩地层标准刻度井群数据,建立了井模型。采用MCNP程序模拟了井中中子和射线的输运,得到了不同地层密度、不同源距处NaI探测器中的混合能谱和非弹能谱。在混合能谱2.5~4.5 MeV能区开窗,混合射线相对计数随源距的变化曲线显示,源距应选择在20~80 cm,密度与混合射线计数之间呈现非线性关系。在非弹能谱1.0~8.0 MeV能区开窗,非弹射线相对计数随源距的变化数据显示,源距应选择在20~40 cm或80 cm附近,密度与非弹射线计数之间成近似线性关系。     

反射率的数值反演

通过分析热流边界条件下的一维热传导过程,提出并实现了由后表面温度变化历史曲线反演前表面反射率变化历史曲线的数值方法。通过一维热传导的正向和反演计算过程,验证了反演程序的可靠性。对数值反演计算和实验测量两种方式得到的反射率曲线进行了对比,结果显示,两条反射率曲线在变化趋势上符合较好,初步验证了一维温度场中数值反演方法的可行性。