NCO异构体结构与分析势能函数

在B3LYP/6-31+G（d）水平上,对NCO分子的各种可能结构进行几何优化,得到了NCO及其异构体分子CNO和CON基态结构都是C_∞v,电子态为X²Ⅱ,NCO分子的平衡核间距R_NC=0.1230 nm,R_CO=0.1186 nm,离解能D_e=13.40 eV,并计算出谐振频率ω₁=1293.44 cm^-1,ω₂（A′）=484.73 cm^-1,ω₂（A″）=559.72 cm^-1,ω₃=1988.41 cm^-1,Renner-Teller参数ε=-0.1429,计算值与实验值吻合较好.在此基础上,应用多体项展式理论,单体项中首次引入开关函数,三体项以NCO,CNO基态结构与性质为依据,拟合给出了NCO分子的基态分析势能函数,其等值势能图准确再现了NCO,CNO分子基态结构与特征,并与优化结果完全一致.     

He-CO相互作用势及散射截面的理论研究

利用改进的MS势模型拟合出了He-CO体系一种形式简单的各向异性相互作用势,应用拟合的势能,采用全量子力学的密耦方法计算了基态氦原子和CO分子碰撞的散射截面,分析并总结了散射截面的变化规律。计算结果表明拟合势能不但表达形式简洁,而且较好的描述了He-CO系统相互作用的特征。为进一步研究He与CO微观碰撞机理有一定的参考价值。     

一种移动式遥测天然气泄漏检测仪

天然气管道泄漏检测对人员安全、环境保护以及国家财产安全等具有重要的意义,但是,由于管线跨越地域广阔,操作工况以及环境情况复杂,致使管线的泄漏检测存在困难。文章介绍了一种基于波长扫描差分吸收光谱技术的移动式遥测天然气泄漏检测仪。针对遥测回波吸收光谱特性,提出了基于小波变换的改进型软阈值小波去噪方法,实验分析能够提高系统信噪比3倍多,同时在遥测光强为530nA时,可达到的最小遥测灵敏度为80ppm.m,系统采用波长扫描差分吸收光谱技术成功实现天然气泄漏的定量遥测与准确定位,具有快速、准确、智能及安全等特点。     

Characteristic ion clusters as determinants for the identification of pyrrolizidine alkaloid N‐oxides in pyrrolizidine alkaloid–containing natural products using HPLC–MS analysis

Pyrrolizidine alkaloid (PA)–containing plants are widely distributed in the world. PAs are hepatotoxic, affecting livestock and humans. PA N‐oxides are often present together with PAs in plants and also exhibit hepatotoxicity but with less potency. HPLC–MS is generally used to analyze PA‐containing herbs, although PA references are unavailable in most cases. However, to date, without reference standards, HPLC–MS methodology cannot distinguish PA N‐oxides from PAs because they both produce the same characteristic ions in mass spectra. In the present study, the mass spectra of 10 PA N‐oxides and the corresponding PAs were systemically investigated using HPLC–MS to define the characteristic mass fragment ions specific to PAs and PA N‐oxides. Mass spectra of toxic retronecine‐type PA N‐oxides exhibited two characteristic ion clusters at m/z 118–120 and 136–138. These ion clusters were produced by three unique fragmentation pathways of PA N‐oxides and were not found in their corresponding PAs. Similarly, the nontoxic platynecine‐type PA N‐oxides also fragmented via three similar pathways to form two characteristic ion clusters at m/z 120–122 and 138–140. Further application of using these characteristic ion clusters allowed successful and rapid identification of PAs and PA N‐oxides in two PA‐containing herbal plants. Our results demonstrated, for the first time, that these characteristic ion clusters are unique determinants to discriminate PA N‐oxides from PAs even without the availability of reference samples. Our findings provide a novel and specific method to differentiate PA N‐oxides from PAs in PA‐containing natural products, which is crucial for the assessment of their intoxication. Copyright © 2012 John Wiley & Sons, Ltd.     

Pulse inversion ultrasound modulated optical tomography

Pulse inversion acoustic imaging is useful as it allows second harmonic imaging to be obtained with short acoustic pulses. This allows high axial resolution, but removes any overlap in the frequency spectra of fundamental and harmonic. We demonstrate pulse inversion ultrasound modulated optical tomography using an optical speckle based detection method. Inverted and non-inverted acoustic pulses combined with synchronized strobed illumination are applied to an optically scattering medium. Over the acquisition time of a camera, multiple pulses are summed and at the next frame the phase of the ultrasound is shifted by π/2 and the process repeated. Combining the two frames allows a second harmonic signal to be obtained. A reduction in linewidth is observed (DC=9.26 mm, fundamental=4.02 mm, second harmonic=2.43 mm) in line scans of optically absorbing objects embedded in a scattering medium (thickness=16 mm, scattering coefficient=2.3 mm(-1), anisotropy factor=0.938).     

全息光刻中的驻波效应研究

对光刻胶内光强分布进行了计算与模拟, 结果表明, 来自基底的反射光与入射光干涉, 光强在垂直基底的方向上呈现强弱周期性变化, 即驻波效应. 进一步的分析与实验结果表明, 随着基底反射率的增加, 驻波效应变得严重, 进而影响光栅掩模的槽形、占宽比并限制线条高度. 为减弱驻波效应的影响, 尝试了使用减反射膜降低基底反射光强度, 实验结果表明, 在基底与光刻胶之间增加一层减反射膜吸收来自基底的反射光强度, 减弱驻波效应的效果显著. 关键词： 全息光刻 驻波 减反射膜     

NO在Pt（111）表面的振动和离解

基于密度泛函理论和周期平板模型研究了NO在Pt（111）表面的吸附,通过扫描隧道显微镜（STM）的理论计算分析了吸附的结构特征．计算得到的Pt-NO伸缩振动（圪）频率基本保持不变,受阻平动（v3,v4）和受阻转动（us,v6）完全是简并的．采用CI-NEB方法讨论了NO在Pt（111）表面的离解过程,研究结果表明NO在Pt（111）表面的离解比较困难,必须克服2．29eV的能垒．     

基于可调谐半导体激光器吸收光谱的温度测量方法研究

介绍了基于半导体激光器作光源的吸收光谱测温技术研究和开发集成的系统,利用H₂O在1.4μm附近的吸收线对的线强比值来反演温度.介绍了该系统在实验室管式高温上的标定和开放炉管的测量验证,结果显示各设置温度下测量温度波动平均在50 K左右.之后在CH₄/空气预混平焰炉上进行进一步验证,发现在吸收线7153.7 cm^-1长波一侧出现了HITRAN08中未给出的几条H₂O吸收和该吸收线重叠.HITEMP中在这些波长上有对应的吸收线给出,但对另一条选用的吸收7154.354 cm^-1,给出的可对应吸收线中心频率和测量不一致.根据实验测量结果和HITRAN/HIlTEMP的对比,对选择吸收线对的位置和线强等参数继续采用实验室标定结果,并引入HlTEMP中给出的这些高温下表现出来的吸收线参数,在平焰炉不同当量比状态下做了测量对比.     

Quantum cascade laser-based spectrometer for high sensitive measurements of trace gases in air

A quantum cascade(QC)laser-based spectrometer is developed to measure trace gases in air.The proposed spectrometer is tested for N2O,and the results presented in this letter.This system takes advantage of recent technology in QC lasers by utilizing intra-pulse scan spectroscopy,which allows high sensitive measurement.Without calibration gases,the gas concentration can be calculated with scan integration and the corresponding values from the HITRAN04 database.By analyzing the Allan variance,a detection limit of 2 ppb is obtained.Continuous measurement of N2O sampled from ambient air shows the applicability of the proposed system for the field measurements of gases of environmental concern.     

Orbital responses to methyl sites in CnH2n+2 (n=1-6)

Orbital responses to methyl sites in C_nH_2n+2 (n=1-6) are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space. The highest occupied molecular orbital (HOMO) investigations indicate the p-electron profiles in methane, ethane, propane, and n-butane. By increasing the number of carbon-carbon bonds in lower momentum regions, the s, p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space (P≤0.50 a.u.). Meanwhile, the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds, meaning that more electrons have contributed to orbital construction. The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space. An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space. However, such shifts are greatly reduced in the outer valence space. Meanwhile, the opposite energy shift trend is found in the intermediate valence space.