Decay dynamics of excited CS2 and NH3 investigated by femtosecond laser

By using the home-made femtosecond laser system and the time-of-flight mass spectrometer, the decay dynamics of excited carbon disulfide (CS2) and ammonia (NH3) are investigated in real time by pump-probe multiphoton ionization detection. The estimated lifetime constant of the NH3 (A) over tilde (1)A(2)' state (51+/-4 fs) agreed quite well with the literature report. For the first time, the decay lifetime constants of the NH3 (E) over tilde'(1)A(1)' state (937+/-93 fs), the CS2 (a) over tilde (3)A(2) state (153+/-10 fs), and the CS2 Rydberg state [(3)/(2)]6ssigma(g) ((3)Pi(g)) (948+/-23 fs) are obtained.

人工小叶锦鸡儿(Caraganamicrophylla)灌丛土壤水分动态研究

采用由植被空间序列推断时间系列的方法 ,分析了 1984、1987、1995和 1999年建立的人工小叶锦鸡儿固沙植被土壤水分的时空变化特征 .结果表明 ,受沙地土壤机械组成的影响 ,沙地土壤组成以物理性沙粒为主 ,>0 .0 1mm沙粒占 97%以上 ,凋萎湿度为 1.5 5 % ,田间持水量为 5 .5 % ,土壤最大有效水为3.95 % .随着固沙植被优势度的增加 ,小叶锦鸡儿灌丛下土壤含水量持续下降 ,1984年建立的植被区土壤含水量明显低于 1999年建立的植被区 ;在年内土壤水分季节变化中 ,4个阶段植被区土壤水分状况在 4～6月不断降低 ,到 6月达到最低值 ,7～ 10月逐渐回升 ;对于建立较早的植被区 (1984和 1987年 ) ,土壤水分垂直变化表现出随着土层深度的增加 ,土壤含水量逐层递减的趋势 ,特别是 70cm下土层中 ,土壤含水下降明显 ,含水量低于凋萎湿度 ;由于对根际区域土壤水分的利用 ,加剧了固沙植被区深层土壤 (70cm下 )水分的亏缺 ,进而影响植被物种的组成 ,随着小叶锦鸡儿灌丛年龄的增加 ,浅根性植物所占比重增加 .

Determination of ascorbic acid by flow injection chemiluminescence suppression method

chemiluminescence suppression method for the determination of ascorbic acid based on Luminol-KIO4-H2O2-ascorbic acid system was established. The linear range for ascorbic acid is 1.0 x 10(-7) similar to 1.0 x 10(-5) mol/L and the detection limit is 6.0 x 10(-8) mol/L. The relative standard deviation (n = 11) is 1.0% for 8.0 x 10(-7) mol/L ascorbic acid. The method has been used to determine the content of ascorbic acid in tablets and injections with satisfactory results.

流动注射化学发光抑制法测定抗坏血酸

基于抗坏血酸对Ｌｕｍｉｎｏｌ－ＫＩＯ４－Ｈ２Ｏ２体系化学发光反应的抑制作用，建立了化学发光抑制快速测定抗坏血酸的新方法。该方法线性范围为 １．０ × １０－７～ １．０ × １０－５ ｍｏｌ／Ｌ，检出限为６．０× １０－８ｍｏｌ／Ｌ，对８．０× １０－７ｍｏｌ／Ｌ抗坏血酸 １１次平行测定的相对标准偏差为 １．０％。用于维生素Ｃ片剂及注射液中抗坏血酸含量的测定，结果令人满意。

Effects of molecular weight and interaction parameter on the glass transition temperature of polystyrene mixtures and its blends with polystyrene/poly(2,6-dimethyl-p-phenylene oxide)

The glass transition temperature (T-g) of mixtures of polystyrene (PS) with different molecular weight and of blends of poly(2,6-dimethyl-p-phenylene oxide) (PPO) and polystyrene with different molecular weight (DMWPS) was studied by a DSC method. For the whole range of composition, the curves of T-g vs composition obtained by experiment were compared with predictions from the Fox, Gordon-Taylor, Couchman and Lu-Weiss, equations. It was found that the experimental results were not in agreement with those from the Fox, Gordon-TayIor and Couchman equations for the binary mixtures of DMWPS, where the interaction parameter chi was approximately zero. However, for the blends PPO/DMWPS (chi < 0), with an increase of molecular weight of PS, it was shown that the experimental results fitted well with those obtained from the Couchman, Gordon-Taylor and Fox equations, respectively. Furthermore, the Gordon-Taylor equation was nearly identical to the Lu-Weiss equation when \chi\ was not very large. Further, the dependence of the change of heat capacity associated with the glass transition (Delta C-p) on the molecular weight of PS was investigated and an empirical equation was presented. (C) 1997 Elsevier Science Ltd.

Studies on structure-property relationship between color reagents and contrast of their color reactions with cerium by topological indices

In this paper, three topological indices A(m1), A(m2) and A(m3) have been applied to multivariate analysis in structure property relationship studies. The topological indices oi fourty-three asymmetrical phosphono bisazo derivatives of chromotropic acid have been calculated, The structure-property relationship between color reagents and contrast of color reactions with cerium has been studied by A, indices and structure selective factors, Good results have been obtained.

拓扑指数法研究稀土显色剂结构与铈显色反应对比度的关系

计算了４３种不对称变色酸双偶氮膦酸型显色剂的Ａ_ｍ拓扑指数，并将其与结构选择性因子相结合，用于偶氮类显色剂结构与铈显色反应对比度的相关性研究，讨论了显色剂结构对拓扑指数及对比度的影响。

铕和铽与3,4-呋喃二甲酸双核配合物的合成、表征及其晶体结构

本文首次合成了铕(Ⅲ)和铽(Ⅲ)与3,4-呋喃二甲酸配合物,研究了它们的IR、DTA、TG、DTG和荧光光谱等性质,并完成了单晶的晶体分析。结果表明,配合物为〔Ln·HL_2(H_2O)_2〕_2·2H_2O(Ln=Eu(Ⅲ),Tb(Ⅲ);H_2L=3,4-呋喃二甲酸),属单斜晶系,P2/c空间群,Z=2,晶胞参数对铕和铽配合物分别为α=10.842(1),10.801(4);b=8.725(2),8.664(2);c=16.366(4),16.308(6)A;β=93.50(1),93.67(3)°;V=1545.3(5),1523.0(8)A~3。

有限元结构动力分析的广义特征值的神经计算

广义特征值问题是结构动力分析计算的关键之一.应用Reyle igh极小值原理,将神经网络的能量函数的极小点对应于广义特征值问题的最小特征值所对应的特征向量,在神经网络朝着能量函数极小点运动的同时得到了最小特征值所对应的特征向量的精确解答.从特征值的变分特性出发,给出了基于罚函数法的其他特征值的神经网络求解方案,从而在理论上给出了广义特征值问题的所有特征值的神经网络求解方法.仿真计算表明,该方法正确、有效可行.

三维荧光光谱研究溶解有机质与汞的相互作用

随着荧光光谱技术的进展 ,三维荧光光谱被广泛应用于研究各种天然水体中溶解有机质 (包括腐殖质 )的各种环境行为 .本文利用三维荧光光谱和荧光猝灭滴定技术研究河流溶解有机质与Hg(Ⅱ )的相互作用 .结果表明 ,溶解有机质中含有的3种类型荧光基团都能够不同程度地被Hg(Ⅱ )猝灭 ,并采用非线性回归分析拟合出Hg(Ⅱ )与 3种荧光基团之间的条件稳定常数 .pH值对Hg(Ⅱ ) DOM体系具有显著影响 .Cl-对Hg(Ⅱ ) DOM体系具有强烈的竞争作用 .Ca(Ⅱ )能够 使Hg(Ⅱ ) DOM体系荧光增强 ,而Mg(Ⅱ )对之影响很小 .此外 ,Cu(Ⅱ )与Hg(Ⅱ ) 都是DOM的荧光猝灭剂 ,但是其猝灭机理存在差异