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1.
K. Chen M. S. Zhang W. C. Chen Q. Chen 《Progress in Crystal Growth and Characterization of Materials》2000,40(1-4):43-50
Raman scattering and photoinduced light scattering in Co-, Cr- and Fe-doped lithium niobate were examined. The A1(TO) modes appear in E symmetry spectrum of the doped lithium niobate. Their intensities vary with different dopings. In the spectrum of z(yy)x geometry, the properties of the lowest-frequency E(TO) mode of the Cr-doped lithium niobate are different from those of pure, Co- and Fe-doped lithium niobate. The intensity of the A1(TO) mode at 637cm-1 I is decreased in doped lithium niobate compared with the pure crystal. We attribute these properties to both the photorefractive effect which is enhanced by dopants and to the different occupation of the doping ions. A light climbing effect was observed in Co- and Cr-doped lithium niobate for the first time. A higher photodamage threshold and quicker light climbing speed were found in Co- and Cr-doped lithium niobate in comparison with the light climbing effect in the Fe-doped lithium niobate. The results from the photoinduced light scattering experiments were compared with those from a Raman spectroscopic study. 相似文献
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运用多体微扰理论方法 ,对开壳层钠原子的内壳层电子的光电离过程2p63s→ 2p5 3skl中分波散射截面和角分布参数进行了计算 .在计算中包括了 2s→ 3p的共振结构 .同时利用多体微扰理论的图式 ,对主要的电子关联相互作用进行了分析 ,并对RPA和BO关联的主要贡献项计算达到了无穷级近似 .计算结果与实验吻合较好 . 相似文献
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K. Tsuruta;A. Omeltchenko;R. K. Kalia;P. Vashishta 《Europhysics letters》1996,33(6):441-446
Sintering of nanoclusters is investigated with the molecular-dynamics approach. At2000 K thermally rough nanocrystals develop an asymmetric neck in 100picoseconds. The neck contains more fourfold than threefold coordinated Si atoms.Amorphous nanoclusters develop a symmetric neck which has nearly equal number ofthreefold and fourfold coordinated Si atoms. In both cases, sintering is drivenby surface diffusion of Si and N atoms. The diffusion is much more rapid in theneck joining amorphous nanoclusters than in the neck region of nanocrystals.https://doi.org/10.1209/epl/i1996-00359-2 相似文献
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《Radiation Physics and Chemistry》2009,78(10):859-873
The current status of the Geant4 toolkit and the recent developments for the geometry, electromagnetic and hadronic physics for medium and high energy are presented. The focus of many recent improvements of the toolkit are key applications including the simulation of large Hadron collider (LHC) experiments at CERN. These developments and physics model extensions provide new capabilities and improvements for other applications of the toolkit for radiation studies in high energy physics (HEP), space and medical research. 相似文献
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《Radiation Physics and Chemistry》2009,78(10):874-881
Compact neutron detectors are being designed and tested for use as low-power real-time personnel dosimeters. The neutron detectors are pin diodes that are mass produced from high-purity Si wafers. Each detector has thousands of circular perforations etched vertically into the device. The perforations are backfilled with 6LiF to make the pin diodes sensitive to thermal neutrons. The prototype devices deliver 4.7% thermal neutron detection efficiency while operating on only 15 V, showing a 9% increase in efficiency over identical planar devices. 相似文献
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多孔硅-导电聚酯材料复合发光器的光学特性研究 总被引：2，自引：0，他引：2
poly-4-dicyanomethylene-4H-cyclopenta[2,1-b:3,4-b]dithiophene monolayer(PCDM)是一种导电,低导带聚酯材料。如果在多孔硅纳米结构中附上一层以自组方式生成的PCDM单分子层,就可以制成能够产生稳定电致发光的器件。发光器的结构是金／PCDM／多孔硅／硅／铝,发光器的电致发光,在白天可用肉眼观察到。有很宽的发光波长,几乎覆盖了整个可见光区域且峰值位于650nm,发光器的面积为1cm^2,启动正向电压在14－30V,电流约300mA。经长时间测试,发光器的稳定性很好,在空气中放置3个月,在输入功率不变的情况下,发光强度也不发生变化,当施以反向电压时,样品仍可以发光而且稳定性较高,在250h内I－V未发生明显变化,扫描电镜图像显示PCDM覆盖的表面要比多孔硅表面平整,而PCDM分子有可能进入到多孔硅纳米孔径当中去,起到了提高发光器稳定性和延长其寿命的作用。 相似文献
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纳米碳管的电化学贮锂性能 总被引：5，自引：0，他引：5
用透射电镜、高分辨透射电镜、X射线衍射和拉曼光谱表征了用催化热解法制备的纳米碳管的结构,研究了纳米碳管的电化学嵌脱锂性能。以纳米级铁粉为催化剂热解乙炔气得到的纳米碳管石墨化程度较低,结构中存在褶皱的石墨层、乱层石墨和微孔等缺陷,具有国交高的贮锂容量,初始容量为640mAh/g,但循环稳定性较差。而以纳米级氧化铁粉为催化剂热解乙烯得到的纳米碳管结构比较规则,循环稳定性较好,但贮锂容量较低,初始容量为282mAh/g。讨论了纳米碳管的结构对其温度特性和不同电流密度下的充放电容易的影响。 相似文献
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The nonperturbative quantum electrodynamies method proposed by Fu et al. [Phys. Rev. A 75 （2007） 063419] is employed to study the high-order above-threshold ionization （ATI） of a diatomic molecule. Based on this frequency-domain theory, the high-order ATI process can be regarded as ATI followed by laser-assisted collision, where the total transition amplitude is the coherent summation of the contributions from each ATI channel. The angular-resolved ATI spectrum, which agrees with the results by Becket et al. based on the time-domain method, is obtained by this frequency domain theory. Furthermore, it is demonstrated that the interference characteristics representing the molecular structure in the ATI spectrum originates from the recollision of the electron with two-centre ion in each ATI channel. 相似文献
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The generation of high order harmonics from an inhomogeneous ovderdense plasma target irradiated by an ultrashort intense laser pulse is studied by numerical simulation. During such interaction, ultrafast electron bunches are generated and excite electron plasma oscillations as they pass through the overdense target. These plasma oscillations will emit high-frequency electromagnetic emission by linear mode conversion. Instead of the integer harmonies generation, the emission appears with a broadband and even continuous spectrum corresponding to the electron plasma frequency range of the inhomogeneous plasma density. 相似文献