Wavelength modulation diode laser absorption spectroscopy for high-pressure gas sensing

A general model for 1f-normalized wavelength modulation absorption spectroscopy with nf detection (i.e., WMS-nf) is presented that considers the performance of injection-current-tuned diode lasers and the reflective interference produced by other optical components on the line-of-sight (LOS) transmission intensity. This model explores the optimization of sensitive detection of optical absorption by species with structured spectra at elevated pressures. Predictions have been validated by comparison with measurements of the 1f-normalized WMS-nf (for n = 2–6) lineshape of the R(11) transition in the 1st overtone band of CO near 2.3 μm at four different pressures ranging from 5 to 20 atm, all at room temperature. The CO mole fractions measured by 1f-normalized WMS-2f, 3f, and 4f techniques agree with calibrated mixtures within 2.0 %. At conditions where absorption features are significantly broadened and large modulation depths are required, uncertainties in the WMS background signals due to reflective interference in the optical path can produce significant error in gas mole fraction measurements by 1f-normalized WMS-2f. However, such potential errors can be greatly reduced by using the higher harmonics, i.e., 1f-normalized WMS-nf with n > 2. In addition, less interference from pressure-broadened neighboring transitions has been observed for WMS with higher harmonics than for WMS-2f.     

TiO2 Nanotube Array/Monolayer Graphene Film Schottky Junction Ultraviolet Light Photodetectors

Schottky junctions made from a titanium dioxide nanotube (TiO₂NT) array in contact with a monolayer graphene (MLG) film are fabricated and utilized for UV light detection. The TiO₂NT array is synthesized by the anodization and the MLG through a simple chemical vapor deposition process. Photoconductive analysis shows that the fabricated Schottky junction photodetector (PD) is sensitive to UV light illumination with good stability and reproducibility. The corresponding responsivity (R), photoconductive gain (G), and detectivity (D*) are calculated to be 15 A W^?1, 51, and 1.5 × 10¹² cm Hz^1/2 W^?1, respectively. It is observed that the fabricated PD exhibits spectral sensitivity and a simple power‐law dependence on light intensity. Moreover, the height of the Schottky junction diode is derived to be 0.59 V by using a low temperature I–V measurement. Finally, the working mechanism of the TiO₂NT array/MLG film Schottky junction PD is elucidated.     

气相中Fe+催化CO与N2O循环反应的理论计算研究

采用密度泛函UB3 LYP/6-311+ G(2d)方法研究了Fe+在基态和激发态与CO与N2O反应的反应机理.全参数优化了反应势能面上各驻点的几何构型,用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证,并用UB3LYP/6-311++G(3df,3pd)、单点垂直激发等方法分别进行各驻点单点能校正,四重态和六重态反应势能面交叉点CP确定,计算结果表明,该反应为两步反应,且反应机理都为插入一消去反应,势能面上的两个交叉点能够有效降低反应的活化能,这在动力学和热力学上都是有利的.     

飞秒激光剥蚀-多接收电感耦合等离子质谱原位微区分析青铜中铅同位素组成-以古铜钱币为例

建立了飞秒激光剥蚀-多接收电感耦合等离子质谱(fLA-MC-ICPMS)铅同位素原位微区分析方法,分别利用溶液法(SN-MC-ICPMS)和激光剥蚀法(fLA-MC-ICPMS)对15个铜(黄铜,青铜)国家标准物质进行了实验分析,测试的结果表明CuPb12(GBW02137)中Pb同位素组成非常均一,可作为以铜为基体的青铜、黄铜及铜矿中Pb同位素原位微区分析的外部参考物质。对CuPb12进行了112次fLA-MC-ICPMS Pb同位素分析测试,其加权平均值与溶液法测定的Pb同位素比值在2σ误差范围内完全一致,208 Pb/204 Pb和207Pb/206Pb比值的内部精度RSE分别小于90和40ppm,外部精度RSD分别小于60和30ppm。利用本实验室建立的fLA-MC-ICPMS分析方法对13个古铜钱币中Pb同位素进行了原位微区无损伤分析,测试结果表明,不同朝代古钱币中Pb同位素组成差异较大,即使同一朝代的古钱币其Pb同位素组成也不尽相同。     

潘宁源放电的全三维电磁粒子模拟/蒙特卡罗碰撞数值算法研究

深入研究潘宁放电的物理机制, 研制了全三维高品质算法粒子模拟软件(PIC), 设计并添加了相应物理情景的蒙特卡罗碰撞模块(MCC), 并对电子、氢分子离子(H₂⁺)、氢正离子(H⁺)、氢三正离子(H₃⁺)同时进行了跟踪, 成功研制了全三维电磁PIC/MCC数值算法. 结合国内研究较热的潘宁放电模型, 对该算法进行模拟验证. 模拟结果显示: 采用有效的滤波算法能抑制电磁数值噪声, 电子能量呈麦克斯韦分布, 由于电子的径向漂移和加速导致离子源顶端H₂⁺产量较大. 关键词： 潘宁离子源 高品质算法 粒子模拟/蒙特卡罗     

结直肠癌细胞株及细胞核的傅里叶变换红外光谱研究

运用傅里叶变换红外光谱技术研究了正常组织(30例)和细胞株(SW 620),正常细胞核和癌变细胞核的红外光谱特征,为红外光谱诊断结直肠癌奠定了细胞及亚细胞水平的实验基础。将所得光谱图的峰位及峰强比进行统计分析发现:细胞株(SW 620)和癌变细胞核中谱带(2 925,1 240和1 085cm-1)的峰位均向高波数移动(p<0.05),而谱带1 400cm-1的峰位均向低波数移动(p<0.05);细胞株(SW 620)中峰强比(I1 650/I1 460,I1 400/I1 460,I1 240/I1 460,)较正常组织升高(p<0.05),而I1 740/I1 460则降低(p<0.01)。癌变细胞核中(I1 650/I1 460,I1 400/I1 460,I1 240/I1 460)较正常细胞核亦升高(p<0.05).这些差异可作为区别组织良恶性的指标。     

非线性介质中强光对弱光聚焦的控制研究

从理论和实验上分析了强光控制弱光脉冲聚焦的方法, 该方法可以灵活地控制弱光的聚焦过程和特性. 通过研究两光束共同传输, 利用强抽运光在相互作用时为弱探测光提供诱导非线性效应, 从而使弱探测光发生聚焦. 得到了在抽运光保持不变情况下探测光的解析解, 并在实验上得到验证. 进一步研究了强抽运光对弱探测光焦点位置的影响. 结果显示: 通过改变抽运光功率、束宽能够有效地控制弱探测光的聚焦过程和焦点位置. 关键词： 诱导聚焦 自聚焦 非线性折射率     

Signatures of reactive resonance: three case studies

 Recent advances in the study of short-lived reactive resonances are reviewed. Special emphasis is given to addressing the question of how reactive resonances might be observed in molecular beam scattering experiments. Three case studies are presented for simple triatomic systems that are believed to exhibit resonance phenomena: F + HD → D + HF, F + H₂ → H + HF, and H + HD → D + H₂. It is seen that reactive resonances do strongly influence collision observables, but in a different way for each case. At this stage, there does not appear to be a unique resonance signature that can be applied to all reactions. Received: 2 March 2002 / Accepted: 2 June 2002 / Published online: 17 October 2002 Acknowledgements. For their valuable input into the research discussed here, we are grateful to our collaborators, K. Liu, S.H. nk;Lee, F. Dong, D.E. Manolopoulos, D, Skouteris, X. Yang, S. Harich, D. Dai, and C.C. Wang. This work was supported by the National Science Foundation. Correspondence to: R. T. Skodje e-mail: skokje@spot.colorado.edu     

原子距边矢量、三键数与烷烃的13C NMR化学位移

提出一个新的原子描述符-原子距边矢量(μ)来表达碳原子在烷烃中所处环境信息,用该矢量和三键数作为参数与烷烃碳原子(含2~9个碳原子共63个烷烃分子,计326个不等价碳原子)的¹³C NMR化学位移相关联,得到的多元线性回归分析结果为:标准偏差S仅0.9629ppm,相关系数R为0.9957.用所得线性方程预测得精度为:误差在1.0,1.5和2.0ppm以内的分别占83%,90%和95%.     

Fractal Dimension of Julia Set for Nonanalytic Maps

The Hausdorff dimensions of the Julia sets for nonanalytic maps f(z) = z ²+εz* and f(z)=z*²+ε are calculated perturbatively for small ε. It is shown that Ruelle's formula for the Hausdorff dimensions of analytic maps cannot be generalized to nonanalytic maps.