82 resultados para 144-879A


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We propose a new x-ray laser mechanism that uses radiation from the strongest 3d --> 2p Ne-like resonance line in an optically thick plasma to radiatively drive population from the Ne-like ground state to the 3d state, which then lases to two 3p states. Collisional mixing of the 3p states with nearby 3s and 3d states depopulates the lower laser states. Modeling is presented for this mechanism in Ne-like Ar, and in experiments we observe one potential 3d --> 3p lasing transition at 45.1 nm in Ne-like Ar. (C) 1996 Optical Society of America

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介绍了近年来硬X射线位相衬度成像技术的发展状况,详细论述了X射线干涉相衬、衍射增强相衬,类同轴相衬等几种典型的成像原理。

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研究了5种新型的具有不同结构的aα-异噁唑偶氮基-β-二酮类衍生物的红外光谱和紫外光谱,讨论了它们的酮式-烯醇式以及偶氮式.腙式之间的互变异构化现象。结果表明,所有化合物无论以固体形式或在溶液中均以腙式二酮体和偶氮式烯醇体的混合形式存在。各化合物的紫外吸收谱均呈双峰状,峰值分别处于246~262nm和326~339nm之间,其中,高波长吸收峰的强度明显高于低波长吸收峰强度,说明了各化合物中偶氮式烯醇体形式均多于腙式二酮体形式,其原因是由于各化合物中偶氮式烯醇体的异构体较多,且易以分子内氢键形式形成六元环,

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概述了绿松石的使用历史和产地来源。利用质子激发X射线荧光光谱(PIXE)、X射线衍射(XRD)及扫描电镜(SEM)技术对来自伊朗、湖北郧县和西藏等地的绿松石样品进行岩石矿物学特征分析,从成分组成方面探讨绿松石的呈色机理。结果显示,不同产地、不同质地绿松石的成分组成存在较大差别,但主成分含量基本一致;绿松石的颜色主要由其中CuO和Fe2O3的含量比值变化决定,比值由大至小,实现了绿松石颜色由天蓝色到绿色的转变。

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Er3+/Yb3+ cocloped fluorophosphate glasses were prepared and their thermal stabilities, Raman spectra, absorption spectra, and fluorescence spectra were measured. It is found that proper content of NaF or PbF2 is helpful for the increase of stability against crystallization. The variation of AI(PO3)3 or NaF content in the composition affects not the maximum phonon energy but the phonon density. The introduction of PbF2 decreases the phonon energy slightly. Intense green and red upconversion luminescence was observed for the fluorophosphate glass with low phosphate content. A glass matrix for upconversion luminescence requiring neither expensive raw material nor special atmospheric conditioned preparation is provided. Infrared luminescence around 1530 nm was researched. Fluorophosphate glasses with bandwidth properties and stimulated-emission cross sections better than tellurite, germanate and silicate glasses are obtained. Through the introduction of NaF, the bandwidth properties are decreased. Through the introduction of PbF2 the gain properties are increased. On the whole, it is difficult to obtain a material with the best gain properties and bandwidth properties simultaneously. There should be a compromise between them according to the demand. (C) 2006 Elsevier B.V. All rights reserved.

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铈掺杂稀土焦硅酸盐系列晶体Re2Si2O7(其中Re=Lu3+、Y3+、Gd3+等)作为新型无机闪烁晶体材料,近来引起科研人员的关注。本文阐述了稀土焦硅酸盐系列晶体Re2Si2O7的结构、晶体生长方法、闪烁性能和有待进一步研究的问题。

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作为发射在1μm波段的二极管抽运全固态激光器的增益介质,掺Yb离子的晶体备受关注。掺Yb晶体具有能级结构简单,量子缺陷低(〈0.1),量子效率高等优点。目前成功使用掺Yb的晶体作为增益介质的飞秒激光振荡器已有很多报道,如Yb:BOYSE,Yb:KYW,Yb:SYSE等。

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