Measurement of angular distribution of M shell fluorescent X-rays excited by 5·95 keV photons in thorium

The differential cross-sections for the emission of M shell fluorescent X-rays from Th by 5·95 keV photons at eight angles ranging from 50° to 120° have been measured. The differential cross-section is found to decrease with increase in the emission angle showing anisotropic spatial distribution of M shell fluorescent X-rays. The present results contradict the predictions of the calculations of Cooper and Zare [1] that the atomic inner shell vacancy states produced in photoionization are not aligned but confirm those of Fluggeet al [2] and Scofield [3] that the vacancy states withJ > 1/2 are aligned. The integral M shell fluorescent emission cross sections have been determined from the measured angular distribution coefficients and compared with theoretical integral cross-sections calculated by using theoretical values of M subshell photoionization cross-sections, fluorescence yields and coster kronig transition probabilities available in literature. The experimental and theoretical values of integral crosssections show a reasonable agreement.     

激光等离子体能量角分布及吸收定标律

主要研究激光平面靶等离子体发射能量角分布及吸收定标律。实验利用高斯型1.06μm激光脉冲,其能量为2～50J,脉冲宽度为0.3～2.2ns,靶面平均辐照强度为1.8×1013～1.1x10~(15)W/cm~2,光束以25°角入射。实验采用了Au、Ag、Ti、Al和C_8H_8等厚靶。用等离子体卡计测量靶面吸收的激光能量。用指数函数拟合实验数据,给出了吸收效率分别作为激光强度、脉冲宽度和靶材料原子序数的函数的定标关系式。这些关系式定性地与逆轫致吸收的理论关系式相一致。     

行列可交换不相关随机变量组列的中心极限定理之收敛速度

（ｘｉｊ）为行列可交换不相关随机变量组列,本文讨论ｓｕｐ│ｐ（ａ＾－１ｎＴｎ〈ｘ）－Φ（ｘ）│→０的速度（其中Ｔｎ＝１／ｎ２ｎΣｉ＝１ｎΣｊ＝１ｘｉｊ,Ｏ＾２ｎ＝ＶａｒＴｎ,Φ（ｘ）为标准正态分布函数）,取得了与Ｕ－统计量情形下相同的结果。     

独立随机变量部分和的大偏差概率的估计

设｛Ｘｎ｝ｎ≥１是一列相互独立且具有相同分布、非负非退化的随机变量序列．Ｓ＝Ｘ１＋…＋Ｘｎ，μＥＸ１，ａ是Ｘ１的分布支撑的上确界．假设ＥｅｕＸ１＜∞，ｕ＞０．对μ＜Ｘｎ＜ａ，本文分别讨论了１ｏｇＰ｛Ｓｎ≥ｎｘｎ｝及Ｐ｛Ｓｎ≥ｎｘｎ｝Ｊ当ｎ→∞时的渐近性质。     

带双参数的非线性椭园型本征值问题

本文利用变分方法，将带双参数的非线性椭园本征值问题转化为约束极值问题，得出了非线性本征值问题的分歧解的存在性。     

TDPAC studies of Hf doped YBCO

Time differential perturbed angular correlation measurements of the 133–482 keVγ-γ cascade of¹⁸¹Ta in Hf-doped YBa₂Cu₃O_7−x are presented. The¹⁸¹Hf precurser nuclei are incorporated into the sample by thermal neutron irradiation. Two quadrupole interaction frequencies are observed in the as-irradiated sample:v _Q1=161±10 MHz with intensityf ₁=75%, asymmetry parameterη ₁=0.32 and damping parameter Λ₁=0.42, andv _Q2=1108±40 MHz withf ₂=25%,η ₂=0.62, and Λ₂=0.60. On annealing the sample in air at various temperaturesT _a and quenching to room temperature,f ₁ remained nearly constant forT _a<600°C andv _Q1 for all annealing temperatures indicating that these are insensitive to oxygen stoichiometry. This frequency is interpreted to be due to¹⁸¹Hf substitutingY sites. BeyondT _a=600°C,f ₁ increased and reached a constant value of 90% forT _a=800°C. The value ofv _Q2 showed a slight variation between 1086 and 1160 MHz, whilef ₂ remained nearly constant at 25% forT _a<600°C. This component is identified to be due to¹⁸¹Hf substituting Cu 1 sites in the Cu-O chains of YBCO. Above 600°Cv _Q2 decreased and reached a value of 808 MHz beyond 750°C.     

非保守动力学系统的Noether定理的一个证明

本文直接从动力学系统的Lagrange函数在无穷小变换下的变换性质出发,得到了完整非保守和非完整非保守的Noether定理。本文的方法具有优越性。     

稳态Q-tensor液晶流的Liouville定理

研究了三维空间中稳态Q-tensor液晶流模型,并用试探函数方法证明了当速度场u\in L^{\frac{\mathrm{9}}{\mathrm{2}},\mathrm{\infty }}({\mathrm{R}}^{\mathrm{3}})?\stackrel{·}{H^{\mathrm{1}}}({\mathrm{R}}^{\mathrm{3}}),液晶的张量型序参量\mathit{Q}\in H^{\mathrm{2}}({\mathrm{R}}^{\mathrm{3}})时,该稳态系统只有零平凡解。     

光热敏折变玻璃及其布拉格体光栅特性研究

采用高温二次化料的方法制备了一种SiO2-Al2O3-ZnO-Na2O(F、Br)玻璃体系的光热敏折变(PTR)玻璃,通过紫外曝光、透射率光谱、X射线衍射(XRD)和差热分析等方法研究了其光热敏析晶机理。研究表明,PTR玻璃的光敏区为280～350nm,工作区为400～2700nm,最佳成核温度和析晶温度分别为490℃和595℃,析晶组分为NaF晶体。采用双光束干涉方法与"两步法"的热处理工艺在PTR玻璃中制备了周期为1000mm-1的布拉格体光栅,光栅的相对衍射效率达到91%,并验证了制备的布拉格体光栅具有角选择滤波能力。     

A new method for resolving combinatorial ambiguities at hadron colliders

We present a new method for resolving combinatorial ambiguities that arise in multi-particle decay chains at hadron colliders where the assignment of visible particles to the different decay chains has ambiguities. Our method, based on selection cuts favoring high transverse momentum and low invariant mass pairings, is shown to be significantly superior to the more traditional hemisphere method for a large class of decay chains, producing an increase in signal retention of up to a factor of 2. This new method can thus greatly reduce the combinatorial ambiguities of decay chain assignments.