Yb:FAP和Yb:C_3S_2-FAP晶体光谱的温度特性和选择激发

报导了Yb :FAP和Yb :C3S2 _FAP晶体在不同温度下的吸收光谱和荧光光谱实验结果 ,研究发现由于电子_声子近共振耦合作用 ,Yb :FAP和Yb :C3S2 _FAP晶体均存在有明显的振动谱 ,Yb :FAP晶体的零声子线在低温下还劈裂为相差 10cm- 1 的两条线 .采用激光选择激发技术研究了Yb3 离子在FAP和C3S2 _FAP晶体中的格位特征 ,结果表明Yb3 离子在这两种基质中都只占据Ca(Ⅱ )格位 ,但由于CaF2 的挥发 ,导致了Ca(Ⅱ )格位的局部畸变 .     

Phonon spectrum boron nitrideof single-wallednanotubes

Based on a force constant model, we investigated the phonon spectrum and then specific heat of single-walled boron nitride nanotubes. The results show that the frequencies of Raman and infrared active modes decrease with increasing diameter in the low frequency, which is consistent with the results calculated by density functional theory. The fitting formulae for diameter and chirality dependence of specific heat at 300K are given.     

Propagation characteristics of linearly polarized Bessel-Gaussian beams through an annular apertured paraxial ABCD optical system

By means of Collins diffraction integral formula in the paraxial approximation and based on the fact that a hard aperture function can be expanded into a finite sum of complex Gaussian functions, an approximate analytical expression for linearly polarized Bessel-Gaussian beams passing through a paraxial ABCD optical system with an annular aperture has been derived. The results provide more convenient for studying their propagation and transformation than the usual way by using diffraction integral directly. By using the analytical expression and the diffraction integral formula some numerical simulations are done to illustrate for the propagation characteristics of a linearly polarized Bessel-Gaussian beam through an optical system with an annular aperture.     

小试金富集ICP-AES法同时测定试样中的铂、钯、金

文章报道了用小试金富集ICP AES法同时测定试样中的铂、钯和金 ,将 1 0～ 2 0g试样中的铂、钯、金富集在毫克量的银合粒中 ,制成溶液后用ICP AES法同时测定铂、钯和金。该方法的检出限 (μg·mL-1 )Pt,Pd ,Au分别为 0 0 1 ,0 0 0 5 ,0 0 1 ,相对标准偏差 (RSD ,n =1 0 )分别为 0 1 % ,0 1 2 % ,0 0 9% ,标准回收率均在 97%以上。生产实践表明 ,本方法是一种快速、简便、准确的分析方法 ,已被我们应用于测定样品中的铂 ,钯和金     

Intensity distribution and coherence property for the broadband Gaussian Schell-model array beams in free space

The intensity distribution and the equal-time complex degree of coherence for the broadband Gaussian Schell-model array beams with different bandwidth propagating in free space are analyzed by the numerical calculation. Results show that the intensity distribution for the broadband Gaussian Schell-model array beams by uncorrelated superposition is rarely affected by the bandwidth; the intensity distribution in the far field for the broadband Gaussian Schell-model array beams by correlated superposition is affected by the bandwidth more obviously than that in the near field. With the increasing of the propagation distance, differences in the equal-time complex degree of coherence for the broadband Gaussian Schell-model array beams with different bandwidth become prominent.     

"烧蚀模式"激光推进技术及其应用研究

随着激光技术的发展,激光推进技术越来越受到关注."烧蚀模式"激光推进是激光推进技术中一个重要的研究领域.本文在介绍了"烧蚀模式"激光推进的原理、研究现状和几个亟待解决的热点研究问题的基础上,对激光推进的进一步应用进行了探索与研究.     

Output characteristics of a cataphoresis He–Sr recombination laser

A cataphoresis discharge tube of 7 mm inner diameter and 38 cm active length was designed and made for the He–Sr⁺ laser. The cataphoretic input of uniform distribution of strontium vapor concentrations along the active region was realized by the cataphoresis effect and the slow flowing (0.5 nl/h) of helium buffer gas. The strontium ionic recombination laser at 430.5 nm and the R–M transition laser at 1.03 μm were obtained with the modified Blumlein circuit by high-frequency longitudinal pulsed discharge. The laser components are concentrated on the 430.5 nm wavelength. Dependences of working parameters such as the pulse frequency, the supply voltage, and the helium pressure on laser output characteristics were measured and discussed. The maximum laser output power of 819 mW and specific power of 56 mW/cm³ were obtained, respectively.     

Conductivity exponent in three-dimensional percolation by diffusion based on molecular trajectory algorithm and blind-ant rules

Diffusion on random systems above and at their percolation threshold in three dimensions is carried out by a molecular trajectory method and a simple lattice random walk method, respectively. The classical regimes of diffusion on percolation near the threshold are observed in our simulations by both methods. Our Monte Carlo simulations by the simple lattice random walk method give the conductivity exponent μ/ν=2.32±0.02 for diffusion on the incipient infinite clusters and μ/ν=2.21±0.03 for diffusion on a percolating lattice above the threshold. However, while diffusion is performed by the molecular trajectory algorithm either on the incipient infinite clusters or on a percolating lattice above the threshold, the result is found to be μ/ν=2.26±0.02. In addition, it takes less time step for diffusion based on the molecular trajectory algorithm to reach the asymptotic limit comparing with the simple lattice random walk.     

Ferromagnetism of Ni cluster in Ni-doped ZnO by solid state reaction

Ni-doped ZnO samples with ferromagnetism at room temperature have been prepared by solid state reaction. It is found that the ferromagnetism originates from the nanosized Ni clusters formed from the decomposition of NiO during calcination. The magnetic properties can be explained by the microstructure of sparsely distributed, randomly oriented and magnetically saturated Ni clusters. Experiments show that the addition of Cu ions will block the decomposition of NiO because Cu²⁺ is more likely reduced to Cu⁺. Hall effect confirms the absence of exchange coupling between local spins and charge carriers.     

Modal interferometer based on tapering single-mode-multimode-single-mode fiber structure by hydrogen flame

A modal interferometer is experimentally demonstrated based on tapering a single-mode-multimode-singlemode (SMS) fiber structure heated by hydrogen flame.The interference fringe begins to form when tapering length is 19.8 mm,and becomes regular and clear when the tapering length is longer and the tapered waist diameter is smaller.Annealing process is undertaken to achieve a high extension ratio of approximately 17 dB with free spectral range of 1.5 nm when the tapering length is 33 mm and the tapered waist diameter is approximately 5μm.The temperature and axial strain dependences of the tapered SMS structure are characterized,and the measured temperature and strain coefficients are +7 pm/℃and -9.536 pm/με, respectively.