推荐一个有机化学基础实验:BINOL的合成及拆分

推荐了一种简便、高效的 1,1′ 联 2 萘酚 (BINOL)的合成与拆分方法作为大学有机化学基础实验     

非傍轴平顶高斯光束M2因子两种定义的比较研究

基于功率密度的二阶矩方法,推导出了非傍轴平顶高斯(FG)光束束宽和远场发散角的解析表达式·研究表明,当w0/λ→0时,远场发散角趋于渐近值θmax=63.435°,与阶数无关·使用非傍轴高斯光束代替傍轴高斯光束作为理想光束,研究了非傍轴FG光束的M2因子,并与传统定义的M2因子作了比较·在非傍轴范畴,非傍轴FG光束的M2因子不仅与阶数N有关,而且与w0/λ有关·按照定义,当w0/λ→0时,非傍轴FG光束的M2因子不等于0,对阶数N=1,2,3时,M2因子分别趋于0.913,0.882和0.886·当N→∞时,M2因子取最小值M2min=0.816·     

研究K4-同胚图K4(α,1,1,δ,ε,η)色性的一个引理

主要介绍了一个引理，这个引理奠定了K4－同胚图K4（α，1，1，δ，ε，η）色性研究的基础。     

（Tm,Ho）：YLF晶体激光器的实验研究

报道了一台连续792nmTi:Al2O3激光器纵向抽运的（Tm,Ho):YLF微片激光器。在室温条件下，当抽运功率为680mW时，激光器在2．06μm波长的输出功率达到90mW。激光器阈值为380mW，光光转换效率为13％，斜率效率为26%.     

弱(L_1,L_2)-BLD映射的正则性

本文首先将文［１］中的ＢＬＤ映射推广为弱（Ｌ１，Ｌ２）－ＢＬＤ映射，并证明了如下正则性结果：存在两个可积指数 Ｐ１＝Ｐ１（ｎ，Ｌ１，Ｌ２）＜ｎ＜ｑ１＝ｑ１（ｎ，Ｌ１，Ｌ２），使得对任意弱（Ｌ１，Ｌ２）－ＢＬＤ映射ｆ∈（Ω，Ｒｎ），都有ｆ∈（Ω，Ｒｎ），即ｆ为（Ｌ１，Ｌ２）－ＢＬＤ映射．     

ZnAl2O4/α-Al2O3复合衬底的制备和GaN薄膜的生长

利用脉冲激光淀积法(PLD)在α-Al₂O₃衬底上淀积了ZnO薄膜, 通过ZnO和α-Al₂O₃固相反应制备了具有ZnAl₂O₄覆盖层的α-Al₂O₃衬底. X射线衍射谱(XRD)表明ZnAl₂O₄薄膜随反应时间由单一(111)取向转变为多晶取向, 然后变为不完全的(111)择优取向. 同时扫描电子显微镜(SEM)照片表明ZnAl₂O₄表面形貌随反应时间由均匀的岛状结构先变为棒状结构, 然后再变为突起的线状结构. 另外, XRD谱显示低温制备的ZnAl₂O₄在高温下不稳定. 在ZnAl₂O₄覆盖的α-Al₂O₃衬底上利用光加热低压MOCVD法直接生长了GaN薄膜. XRD测量表明随ZnAl₂O₄厚度增加GaN由c轴单晶变为多晶, 单晶GaN的摇摆曲线半高宽为0.4°. 结果表明薄ZnAl₂O₄覆盖层的岛状结构有利于GaN生长初期的成核, 从而提高了GaN的晶体质量.     

What Is Its Real Existing Form?——Theoretical and Experimental Studies on 2-Mercaptobenzothiazole

1 INTRODUCTION The study of heterocyclic molecules with aroma- tic rings and their absorptions on metals is of con- siderable importance from both theoretical and te- chnological points of view. These molecules are in- teresting because of their applications as corrosion inhibitors and flotation collectors, and their abilities to form self-assembly layers[1]. 2-Mercaptobenzo- thiazole (C7H5NS2, in the following MBT) is an important heterocyclic molecule, which can be used as corrosion …     

Origin of the 420 nm Absorption Band and Effect of Doping Fluorine in PbWO4 Crystals

The electronic structures for three types of PbW04 (PWO) crystals, the perfect PWO, the PWO containing lead vacancy (PWO-Vpb) and fluorine doped PWO crystal (F^-：PWO), are systematically studied within the framework of density functional theory. The computational results show that the Pb 6s state situates below the valence band so that Pb^2 ions are unable to trap holes forming Pb^3 or Pb^4 to compensate for VPb^2-. The hole-trappers in PWO-Vpb are O^2- ions. Two of the longer-bond O^2- ions share a hole forming O2^3-, and four of the longer-bond oxygen ions trap two holes forming an associated color centre [O2^3--Vpb-O2^3-], which may be the origin of the 42Onto absorption band. It is also concluded that the doping of F^- would reduce the band gap and F^- ions substituting for O^2- can effectively restrict the formation of [O2^3--Vpb-O2^3-] and weaken the 42Onm absorption band and hence enhance the scintillation property of PWO.