激光拉曼光谱仪的全系统校正

提出了一套对激光拉曼光谱仪进行全系统校正的完整方案，并在一台ＳＰＥＸ １４３０型双单色仪单道拉曼光谱仪上全面实现了这套校正，包括谱仪的波数精度及重现性，狭缝函数，光谱分辨率，功率传递系数，光谱响应，偏振光谱响应，偏振传递性能及寄生谱带检查。结果表明，在激光拉曼谱测量中许多源于光谱仪体系的测量误差实际上是不可避免的，因此对常用的谱仪要作日常的状态监控和至少一次全面系统校正，是激光拉曼谱学研究的先决条     

Spin-echo length calibration of OffSpec

OffSpec is one of the seven new spectrometers operational from day one in the second Target Station (TS2) at the pulsed spallation neutron source ISIS. OffSpec is a time-of-flight, low-background reflectometer specialized in off-specular scattering. It is unique because in addition to conventional reflectivity techniques, it is capable of using the neutron spin-echo angle labelling technique. One of the many possibilities of using this technique is measuring structures on a surface with the length scale of 20 nm-15 μm. Up to now the calibration of this length scale was made on the prototype instrument in Delft by measuring magnetic line integrals. This showed that the pole shoe design, an essential part of the spin-echo encoding, was not perfect, resulting in a different effective magnetic encoding angle from the physical angle. Recent reflection measurements on gold gratings not only confirmed this but also resulted in a reliable calibration.     

Upgrade of a Raman Spectrometer

Abstract

Improvement of a conventional JEOL Raman spectrometer with a single channel photo multiplier detector is described. New optical components [fibers, mirror, lens, and charge coupled device detector (CCD)] have been chosen to design a high quality and easy‐to‐use instrument. Tests have shown that with this modified spectrometer, Raman spectra can be acquired of a quality comparable to the spectra obtained previously, but the time needed to obtain a spectrum is markedly reduced. Selected test spectra and a simple calibration procedure to obtain the wavenumber values from the band CCD pixel position are presented.     

Raman scattering by folded acoustic phonons in InGaN/GaN superlattices

We use Raman scattering to investigate the folded longitudinal acoustic (LA) phonons in a series of In_xGa_1−xN/GaN superlattices (SLs) grown by molecular beam epitaxy with different compositions (15% < x < 38%) and SL periods (from 8 to 20 nm). A novel, ultralow wavenumber filtering module, which provides access to ultralow wavenumber Raman modes on single‐grating spectrometers, has been used to perform the Raman measurements. Zone‐folding effects are observed, and the wavenumber behavior of the folded LA modes is well reproduced with a linear dispersion for the folded LA modes as predicted by elastic continuum theory. We employ the wavenumber of the doublets to evaluate the period of the SLs. Copyright © 2011 John Wiley & Sons, Ltd.     

New Developments and Applications of Handheld Raman,Mid-Infrared,and Near-Infrared Spectrometers

Abstract: Recently, miniaturization of Raman, mid-infrared (IR), and near-infrared (NIR) spectrometers has made substantial progress. Though mid-infrared systems are based exclusively on attenuated total reflection (ATR) measurements, near-infrared spectrometers operate in the diffuse reflection or transmission mode. The reduction in size, however, must not be accompanied by deterioration in measurement performance, and portable instrumentation will only have a real impact on quality and process control if Raman, IR, and NIR spectra of comparable quality to laboratory spectrometers can be obtained.

In the present communication, a short overview on the building principles of novel handheld systems will be provided and the results of qualitative and quantitative analyses of selected liquid and solid sample systems obtained with these Raman, Fourier transform infrared (FTIR), and NIR spectrometers will be evaluated in terms of their comparability with laboratory instruments and their suitability for on-site and field measurements.     

Accurate intensity calibration for low wavenumber (−150 to 150 cm−1) Raman spectroscopy using the pure rotational spectrum of N2

We report on an accurate intensity calibration method for low wavenumber Raman spectroscopy. It uses the rotational Raman spectrum of N₂. The intensity distributions in the rotational Raman spectra of diatomic molecules are theoretically well established. They can be used as primary intensity standards for intensity calibration. The intensity ratios of the Stokes and anti‐Stokes transitions originating from the same rotational levels are not affected by thermal population. Taking the effect of rotation–vibration interactions appropriately into account, we are able to calculate these intensity ratios theoretically. The comparison between the observed and calculated ratios of the N₂ pure rotational spectrum provides an accurate relative sensitivity curve (error ~5 × 10⁻⁴) in the wavenumber region of −150 to 150 cm⁻¹. We determine the temperature of water solely from the low wavenumber Raman spectra, using a thus calibrated spectrometer. The Raman temperature shows an excellent agreement with the thermocouple temperature, with only 0.5 K difference. The present calibration technique will be highly useful in many applications of low wavenumber quantitative Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

波长色散X射线荧光光谱仪的内部校准

根据波长色散X射线荧光光谱仪检定规程制定了内部校准作业指导书,对PANalytical Axios 4.0型X射线荧光光谱仪的外观、精密度（RSD）、稳定性（RR）、探测器分辨率（流气正比计数器、闪烁计数器、封Xe正比计数器）和仪器的计数线性进行了性能测试和内部校准.     

平场全息凹面光栅制作结构与使用结构之间误差补偿作用的数值模拟与实验验证

通过对优化计算出的平场全息凹面光栅制作结构(曝光记录结构)和使用结构(光谱仪分光结构)之间各个参数进行联合数值模拟,得出如下结论：在优化设计参数值附近一个较大范围的误差区域内,平场全息凹面光栅的制作结构参数误 差和使用结构参数误差可以相互补偿,最终补偿的结果可以使光谱成像质量达到与原设计结构相当的水平,满足光谱仪器的使用要求。文章给出了数值模拟结果以及与其相符的实验验证结果。此补偿作用有利于降低平场全息凹面光栅制作 中各个参数精度的调节难度,并且可以对实际使用过程中光谱仪器的设计和装调进行理论上的指导。     

Direct Determination of Mercury in the Laboratory Atmosphere by Impaction-Electrothermal Atomization Atomic Absorption Spectrometry

Abstract

A single stage impaction system connected to an electrothermal atomization atomic absorption spectrometer will allow a direct and near real time determination of mercury in the laboratory atmosphere to be detected. Practical concentrations of low ng m^? 3 can be detected, with good precision and linearity of calibration curve. The system detected m^? 3 levels of mercury directly and on a near real time in the vicinity of a polarography instrument.     

Reducing the influence of the premonochromator on the stability of fourier spectrometers

A method is proposed to improve the stability of specialized solar Fourier spectrometers. The method is based on matching the premonochromator bandwidth with the Fourier harmonic frequency of the spectrometer. It is shown that this matching is efficient for both decrease of the measurement errors due to premonochromator instabilities and increase of the linearity of the measurement range. Some possible applications of this procedure for slot spectrometers and Fabry-Perot interference filters are considered. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 7, pp. 815–823, July, 1998.     

Precision in Mössbauer Spectroscopy

In this paper the factors which are responsible for precision and reliability of the experimental data are discussed. The detectors of different types are compared with respect to the precision of the final results. It is shown that the use of resonance detectors gives the best results in most cases of the Sn-119m Mössbauer spectroscopy. The estimation of spectral line distortion caused by a short distance between source and detector is presented. Different procedures of velocity scale calibration are discussed. It has to be underlined that Kuprijanov's method of the velocity scale calibration gives the most reliable and fast results.     

食用植物油中反式脂肪酸含量的激光拉曼光谱检测

油脂中的反式脂肪酸(TFA)有害人们的身体健康,有必要对其含量进行监测。共收集各类食用植物油样本79个,涉及9个品种和27个品牌,分配到校正集和预测集的样本数分别为53个和26个。采用QE65000拉曼光谱仪采集79个样本的拉曼光谱,利用自适应迭代惩罚最小二乘法去除样本拉曼光谱的荧光背景;在此基础上,采用多种归一化方法对样本拉曼光谱进行处理,并对拉曼光谱的建模波数范围进行初选;再利用竞争性自适应重加权采样(CARS)方法筛选与食用植物油TFA含量相关的光谱变量,并应用偏最小二乘(PLS)回归将食用植物油TFA的特征变量光谱强度与气相色谱测定的TFA真实含量进行关联,建立食用植物油中TFA含量的定量预测模型。研究结果表明,多种归一化方法中,有4种归一化方法均能提高PLS定量预测模型的性能,其中Area normalization方法的效果最优;经建模波数范围初选,波数范围由686~2 301 cm-1缩减为737~1 787 cm-1,确定较优的建模波数范围为737~1 787 cm-1;经CARS方法筛选,共有31个光谱变量被选择,其选择的光谱变量主要分布在1 265,1 303,1 442及1 658 cm-1拉曼振动峰附近,且974 cm-1拉曼振动峰两侧均有光谱变量被选择;此外,CARS方法的PLS建模结果优于常用的无信息变量消除及连续投影算法。由此可知,激光拉曼光谱技术结合化学计量学方法检测食用植物油中的TFA含量是可行的。归一化方法、建模波数范围初选及竞争性自适应重加权采样(CARS)方法能有效提高TFA定量预测模型的预测精度和稳定性,优化后的TFA定量预测模型的校正集及预测集的相关系数和均方根误差分别为0.949,0.953和0.188%,0.191%。与未优化的预测模型相比,预测均方根误差由0.361%下降为0.191%,下降幅度为47.1%;建模所用的变量数由683个下降为31个,仅占原变量数的4.54%。     

小型宽波段凹面全息光栅单色仪的优化设计

随着户外物性分析实验的日渐增多,开发轻小型、便携式,且响应波段范围宽的光谱仪器的需求越来越迫切。根据凹面全息光栅均方根优化理论,设计了一款轻小型宽波段单色仪。该单色仪主要由三块IV型凹面全息光栅和上下两层可旋转的平台组成,三块光栅对称地固定于上层平台上,由一台步进电机带动上层平台旋转实现光栅之间的切换,另一台步进电机带动下层平台旋转实现单块光栅的扫描。三块光栅的响应波长范围分别为400～1000,1000～1700和1700～2500nm,其理论分辨极限分别优于2.5,2.8和4.0nm。并对三块光栅的制作误差和双层平台结构误差进行了分析,结果表明,在能够保证的误差范围内,该单色仪的光谱质量可以较好地满足户外光谱分析的要求。     

Velocity calibration for in-situ Mössbauer data from Mars

Beginning in August 2004, raw data acquired by the Mössbauer spectrometers on the Mars Exploration Rovers (MERs) have been released to the science community as Experimental Data Records (EDRs) for each Martian day (sol) on which measurements were made. To provide convenient direct access to the EDR data, to enable independent assessment and analysis, and to allow confirmation of MER-team scientific conclusions, a new Windows-based computer program, MERView, has been developed. Direct inspection of the binary structure of an EDR file, conversion of the binary data to decimal column format for display or export, and full-screen graphical displays are included, allowing, in a highly transparent and user-friendly manner, immediate and thorough overview of the entire EDR data set. MERView also includes automated procedures for velocity calibration. Correction for non-linearity is done using the EDR-provided drive error signal, a phase shift, and the requirement that the two halves of a reference spectrum must overlap exactly when plotted on a correct velocity scale. Absolute velocity calibration (mm/s) is then accomplished by comparing each reference spectrum with known peak positions of standard reference materials.     

A statistical study of the analysis of congested spectra by total spectrum fitting

Heavily overlapped, or congested spectra often display much structure but few individual “lines.” Methods have been devised for analyzing such spectra through nonlinear least-squares fitting of the intensity as a function of wavelength or wavenumber. Such total spectrum fitting (TSF) methods are examined statistically for a simple diatomic model and compared with the standard “measure-assign-fit” (MAF) approach in use since the dawn of spectroscopy. Monte Carlo computations on typically 1000 synthetic spectra at a time verify that the predictions of the variance-covariance matrix are reliable under many circumstances. However in regions where the P and R branches double up, the predicted standard errors in the key spectroscopic constants rise sharply and greatly exceed estimates from the Monte Carlo ensemble statistics. In the same regions, the MAF method actually gives better precision. However, for imperfectly overlapped R and P branches, the MAF standard errors are typically three times larger than the TSF values; moreover, the MAF statistical errors are dwarfed by bias. The TSF approach, while clearly superior in these tests, has a practical drawback: it, too, can give significant bias if the spectra are analyzed with an incorrect model, as illustrated here through calculations employing the wrong function to describe the spectral lineshape.     

Use of in-house primary standard blackbodies for accurate cathode temperature measurement

The interpretation of cathode behavior in traveling wave tubes is clouded considerably by the uncertainty in both the precision and absolute accuracy of cathode temperature measurements as determined by optical pyrometry. The sensitivity and potential accuracy of optical pyrometry is very good, but many sources of error are possible. Sources of error that were experimentally measured in this study can be classified in three categories: (a) instrument and calibration errors; (b) operator (subjective) errors; and (c) errors caused by obstacles or geometrical variations in the optical path. Possible methods of avoiding or correcting sources of errors are recommended, including the use of an in-house primary standard blackbody. The design and use of this device are described in detail. When the primary standard is used and coupled to cathode measurements through secondary blackbodies optical pyrometry is an extremely reliable method for cathode temperature determination.     

结合SNV的分段直接标准化方法在拉曼光谱模型传递中的应用

为了实现拉曼光谱在不同仪器上的模型传递,文章提出了一种改进的分段直接标准化算法.该方法先利用标准正态变换法对光谱数据进行处理,以减少源机与目标机之间的光谱背景与强度影响,再采用分段直接标准化算法消除不同仪器间对样本信息反应差异,实现拉曼光谱的全谱传递.此外,还提出了传递误差率指标用于对光谱传递效果的定量评价.针对汽油拉...     

In situ detection of cocaine hydrochloride in clothing impregnated with the drug using benchtop and portable Raman spectroscopy

This study describes the application of benchtop and portable Raman spectroscopy for the in situ detection of cocaine hydrochloride in clothing impregnated with the drug. Raman spectra were obtained from a set of undyed natural and synthetic fibres and dyed textiles impregnated with the drug. The spectra were collected using three Raman spectrometers: one benchtop dispersive spectrometer coupled to a fibre‐optic probe and two portable spectrometers. Despite the presence of some spectral bands arising from the natural and synthetic polymer and dyed textiles, the drug could be identified by its characteristic Raman bands. High‐quality spectra of the drug could be acquired in situ within seconds and without any sample preparation or alteration of the evidential material. A field‐portable Raman spectrometer is a reliable technique that can be used by emergency response teams to rapidly identify unknown samples. Copyright © 2009 John Wiley & Sons, Ltd.     

基于气体特征吸收谱线的太赫兹时域光谱仪频率校准

提出一种基于气体特征吸收谱线的太赫兹时域光谱仪（THz-TDS）的频率校准方法。通过将THz-TDS测量结果与CO在THz波段的特征吸收谱线标准数据进行比较,对THz-TDS光学延时线运动速度控制不精确造成的光谱测量线性误差进行了修正,从而实现了THz-TDS的频率校准,修正后的THz-TDS频率测量平均误差为3.1 GHz。     

基于Ar分支比方法的光谱强度响应效率标定研究

利用Nd∶YAG激光器输出的1 064 nm激光在大气压环境中产生了Ar等离子体,测量了Ar等离子体的发射光谱,从Ar等离子体发射光谱中筛选出了来自Ar Ⅰ和Ar Ⅱ 15个上能级的35条跃迁谱线,基于分支比方法计算了光谱仪的辐射强度响应效率标定系数。此外,利用氘灯和卤钨灯标准光源,对光谱仪辐射强度响应效率进行了标定,得到了针对不同光栅的光谱仪的辐射效率标定系数。用分支比方法获得的辐射强度响应效率标定系数与标准光源得到辐射强度响应效率标定系数具有较好的一致性,其最大相对误差为5.4%。该研究的标定方法可以为一些大型聚变装置的光谱测量的在线标定提供借鉴和参考。