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20 0 1年 ,位于新泽西州穆勒山的贝尔实验室物理奇才詹·亨德里克·舒恩以平均每 8天出 1篇的惊人速度写出论文 .现今 ,依据贝尔实验室 9月 2 5日的报告 :舒恩论文存在许多被指控的不轨行为 (Science杂志2 0 0 2年 10月 4日 ,第 30页 ) .论文被撤消的速度同样惊人 .2 0 0 2年 11月 ,Science刊登了关于舒恩与同事所著的 8篇论文的撤消声明 (见《物理》2 0 0 3年第 2期第 138页 ) .Science杂志电子版对舒恩论文发布相关警告 ,并说将尽快发表书面撤消声明 .在最新的一轮撤消声明大战中 ,美国物理学会 (APS)与美国物理联合会 (AIP)在 2 0 0 … 相似文献
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Surface effect of nanocrystals doped with rare earth ions enriched on surface and its application in upconversion luminescence
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By employing a certain proportion of hydrogen peroxide, ammonia, ammonium fluoride, and ethylene diamine tetraacetic acid (EDTA) as precipitator, well-crystallized LaOF:Eu3+ and LaOF:Yb3+, Er3+ nanocrystals are synthe- sized by using the chemical co-precipitation method. The structural properties of these samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) spectra. The results show that all the samples have an average size below 70 nm, which decreases gradually with the increase of the EDTA content, and a certain number of EDTA molecules are coupled with doped ions on the surfaces of nanocrystals. Most of the doped ions are proved to be enriched on the surfaces of nanocrystals and surrounded by the high energy vibration groups and bonds in EDTA molecules. The observed differences in upconversion emission spectrum among the different LaOF:Yb3+, Er3+ nanocrystals are explained by the different two-photon upconversion mechanisms. Especially, in the LaOF:Yb3+, Er3+ nanocrystals with EDTA, the two-photon processes that contain several special cross-relaxation processes are introduced to analyse the corresponding upconversion mechanisms. 相似文献
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为研究Eu3+:LaF3纳米晶体-液体悬浮系统中局域场效应对荧光辐射寿命的影响,首先用水热法成功制得了粒径均匀、分散性良好的Eu3+:LaF3纳米晶体,通过将其悬浮在各种液体介质中测出了532 nm脉冲激光激发下Eu3+的5D0能级的荧光寿命,该能级的荧光衰减曲线呈明显的二阶指数衰减特征,对荧光寿命的分析表明其中快速荧光衰减部分源于纳米晶体表面附近的稀土离子.荧光衰减的长寿命部分与各种局域场效应理论模型中的最小二乘法拟合结果表明,忽略表面效应并考虑实际的量子效率时,实腔模型是解释本文的研究系统中荧光弛豫的局域场效应的最佳理论模型. 相似文献
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