紫外激光消融有机物的理论和实验研究

本文分析了紫外准分子激光对有机材料的消融过程,用理论模型解释了每个激光脉冲对有机材料的消融量与入射激光能量密度之间的关系.对于有机玻璃.当入射激光能量密度较高时,双光子过程将起主要作用.最后讨论了消融率随有机材料吸收系数之间的关系,对吸收系数较小的材料,消融率随吸收系数改变有一个极大值.     

荧光光谱法研究酸性大红3R与牛血清白蛋白的结合作用

在Tris缓冲溶液(pH 7.4)体系中,运用荧光光谱法和紫外光谱法首次研究了染料酸性大红3R(AS)与牛血清白蛋白(BSA)的相互作用,并考察了表面活性剂对体系荧光强度的影响。结果表明,酸性大红3R与牛血清白蛋白能形成基态复合物,从而导致BSA内源荧光猝灭,猝灭机理主要涉及静态猝灭和非     

小波系数压缩用于柴油十六烷值近红外光谱分析建模

近红外光谱分析建模中存在多变量高维数据处理问题,导致计算量大,不利于过程控制中应用.为此提出利用小波变换压缩近红外光谱数据的算法与准则,并结合柴油十六烷值定量分析研究压缩数据的建模效果.研究表明,经小波方法处理后,变量维数压缩30倍左右,光谱主要信息基本保留,而模型的预测精度和常规预处理方法分析相比有明显提高.光谱数据压缩的同时包含了噪声滤除和基线校正,简化数据处理步骤,有利于NIRS实际应用时提高建模效率.     

TE- and TM-polarization-resolved spectroscopy on quantum wells under normal incidence

We present TE- and TM-polarization-resolved photocurrent measurements on quantum well pin diodes under normal incidence. Usually, optical experiments performed in such a geometry yield information only about transitions involving in-plane (p_x and p_y) components of the hole wave functions because of the in-plane (TE) polarization of the light. Information on transitions sensitive to the p_z components can be obtained by focussing a radially polarized laser beam through a microscope objective with high numerical aperture (NA=0.9). With our setup, the electrical field vector at the focal tail has a significant component along the optical axis (TM-polarization!) which enables excitation of transitions sensitive to p_z components also. Additionally, the existence of a degenerate (azimuthally polarized) optical mode enables switching these p_z components on and off easily.Experimental evidence of these features has been achieved by exploiting the selection rules for e–hh and e–lh transitions in a quantum well structure. We present a comparison of our recorded spectra with theoretical predictions obtained from simple geometric optics assumptions. For our quantum wells the polarization effects are small because our measurement averages the intensity distribution of the whole focal plane. We plan to extend our measurements to polarization resolved single quantum dot spectroscopy. By restricting the detection region to the spatial extent of a single dot, one can exploit the almost pure TM-polarization on the optical axis for obtaining high contrast between heavy- and light-hole exciton absorption.     

Track revelation and optical properties of pentaerythritol tetrakis (allyl carbonate) plastic for application as nuclear track detector: effects of gamma radiations

The etching conditions of an indigenously prepared thin film of pentaerythritol tetrakis(allyl carbonate) (PETAC) were standardised for the use as a nuclear track detector. The optimum etching times in 6?N NaOH at 70°C for the appearance of fission and alpha tracks recorded in this detector from a ²⁵²Cf solid source were found to be 30 min and 1.50?h, respectively. The experimentally determined values for the bulk and track-etch rates for this detector in 6?N NaOH at 70°C were found to be 1.7?±?0.1 and 88.4?±?10.7?µm/h, respectively. From these results, the important track etching properties such as the critical angle of etching, the sensitivity and the fission track registration efficiency were calculated and compared with the commercially available detectors. The activation energy value for bulk etching calculated by applying Arrhenius equation to the bulk etch rates of the detector determined at different etching temperatures was found to be 0.86?±?0.02?eV. This compares very well with the value of about 1.0?eV reported for most commonly used track detectors. The effects of gamma irradiation on this new detector in the dose range of 200–1000?kGy have also been studied using bulk etch rate technique. The activation energy values for bulk etching calculated from bulk etch rates measurements at different temperatures were found to decrease with the increase in gamma dose indicating scission of the detector due to gamma irradiation. The optical band gap of this detector was also determined using UV–visible spectrometry and the value was found to be 4.37?±?0.05?eV.     

茶刺蛾颗粒体病毒色涵体的拉曼光谱研究

得到了茶刺蛾颗粒体病毒(Darna trima Granulosis Virus 缩写为 DtGV)包涵体的拉曼光谱。分析表明,DtGV 包涵体蛋白的二级结构主要为β折叠和无规卷曲,后者含有大量β回折结构;蛋白的所有酪氨酸残基均“暴露”于溶剂中;其 C—C—S—S—C—C 构型属于扭曲—扭曲—扭曲式。     

紫外新激光染料IBOP的研究

本文介绍一种新合成的化合物IBOP.经在多种染料激光器上测试表明,其激光转换效率高,光化学稳定性好,能溶于多种溶剂.性能优于DPS等相同波段的常用激光染料.IBOP在各种溶剂中的激光调谐范围为388～428nm,激光峰值波长在400nm左右.本文给出了IBOP的荧光光谱、吸收光谱、激光特性、溶剂效应和浓度效应等数据,并作了讨论.     

用BBO晶体产生196～228nm波长的紫外辐射

本文报道了用BBO晶体通过混频产生196～228nm可调谐紫外辐射的研究结果.产生200nm及222nm的量子转换效率分别为12%及23%,与理论计算值基本相符.     

紫外可调谐辐射的波长自动跟踪研究

脉冲染料激光器的可见光波段辐射通过共线倍频和非共线混频实现紫外波段的连续可调谐输出.本文报道了一种闭环跟踪方法;在调谐起始波长处,将取样光束在垂直相位匹配方向分割成等光强的两部分,然后在波长调谐时比较和平衡这两部分光强.对该方法在理论上作了分析并在实验中得到成功的验证.获得的自动跟踪效率大于90%.     

基于光谱技术的杨梅汁品种快速鉴别方法的研究

为了实现杨梅汁品种的快速无损鉴别,提出了一种用可见和近红外光谱技术快速鉴别杨梅汁品种的新方法。首先采用偏最小二乘法进行模式特征分析,经过交互验证法判别,确定最佳主成分数为9。完成特征提取后,将这9个主成分作为神经网络的输入变量,建立了三层BP神经网络,实现类别预测的同时也完成了数学建模与优化分析工作。3个品种的杨梅汁样本数均为20,共计60个样本。在神经网络学习中,将其分成训练集样本51个和预测集样本9个。对9个未知样本进行预测,准确率为100％。说明本文提出的基于光谱技术和模式识别的方法具有很好的分类和鉴别能力。