Processing of double-sided interferograms subject to background self-radiation of an FTIR spectrometer

The effect of background (instrumental) self-radiation of a Fourier transform infrared (FTIR) spectrometer on the processing of double-sided interferograms is studied. From a theoretical analysis of the Michelson interferometer it was shown that when the brightness temperature of the object of study is close to the temperature of the instrument, the measured spectrum may contain inverted spectral ranges or isolated bands. The interferogram correction algorithms and experimental technique for elimination of the spectrum inversion and for compensation of the background self-radiation of the instrument are suggested.     

Fourier deconvolution of photoacoustic FTIR spectra

Fourier self-deconvolution is a fairly routine numerical method for increasing the apparent resolution of spectra in which the intrinsic bandwidths are much greater than the instrumental resolution. The present work demonstrates that a photoacoustic (PA) interferogram obtained with a Fourier transform spectrometer can be used directly in this calculation, without the usual intermediate computation of a spectrum. Phase errors in the interferogram must be eliminated as a first step in this procedure. The technique has been applied to PA IR interferograms acquired for an Alberta coal and for kaolinite, a common layer silicate. Several new bands were identified in the coal spectrum and assigned utilizing previously published results for coal. Results for kaolinite illustrate a behaviour characteristic of deconvolution of single bands; in addition, an OH-stretching band usually not detectable in IR spectra of kaolinite was observed and verified by comparison with Raman data.     

Effect of cell resonance on depth profiling in photoacoustic FTIR spectra

Depth profiling by photoacoustic spectroscopy (PAS) is experimentally demonstrated to be feasible in the mid-IR by changing the velocity of the moving mirror in a Fourier-transform infrared (FTIR) spectrometer. The main difficulty in this method originates from resonances of the PAS cell. The modulation frequency bandwidth implicit in an FTIR makes the system very sensitive to such resonances: spurious results are obtained when they are not taken into account. The current experimental investigation has shown that the dependence of resonance behaviour on sample characteristics alters the cell response with different samples, and must be considered in PAS depth profiling.     

Ultra-high resolution 3D NMR spectra from limited-size data sets

The advantage of the filter diagonalization method (FDM) for analysis of triple-resonance NMR experiments is demonstrated by application to a 3D constant time (CT) HNCO experiment. With a 15N-,13C-labeled human ubiquitin sample (1.0 mM), high spectral resolution was obtained at 500 MHz in 25 min with only 6-8 increments in each of the CT dimensions. This data set size is about a factor of 50-100 smaller than typically required, yet FDM analysis results in a fully resolved spectrum with a sharp peak for each HNCO resonance. Unlike Fourier transform (FT) processing, in which spectral resolution in each dimension is inversely proportional to the acquisition time in this dimension, FDM is a true multi-dimensional method; the resolution in all dimensions is determined by the total information content of the entire signal. As the CT dimensions of the 3D HNCO signal have approximate time-reversal symmetry, they can each be doubled by combining the usual four hyper-complex data sets. This apparent quadrupling of the data is important to the success of the method. Thus, whenever raw sensitivity is not limiting, well-resolved n-dimensional spectra can now be obtained in a small fraction of the usual time. Alternatively, to maximize sensitivity, evolution periods of faster relaxing nuclei may be radically shortened, the total required resolution being obtained through chemical shift encoding of other, more slowly relaxing, spins. Improvements similar to those illustrated with a 3D HNCO spectrum are expected for other triple-resonance spectra, where CT evolution in the indirect dimensions is implemented.     

聚丁二炔Langmuir—Blodgett薄膜的光声谱研究：（Ⅰ）结构表征与光声？…

本在用Ｘ－射线小角衍射聚合与转载先后次序不同的ＰＤＡ ＬＢ膜进行结构表征的基础上,不同厚度的ＰＤＡ ＬＢ膜的光声新斩波频率效应说明,随着ＰＤＡ ＬＢ膜厚度增加,ＬＢ膜的热学性质逐渐明显。此外,还探讨了如何从ＰＤＡ ＬＢ膜的光声谱求得光声吸收系数问题,本的研究结果表明,光声谱技术是研究ＬＢ膜热学特性的有效手段。     

Irbesartan: FTIR and Raman spectra. Density functional study on vibrational and NMR spectra

Arterial hypertension is a very common disease, which is treated with different medications such as Irbesartan. This compound is a nonpeptide antagonist of the receptor of the enzyme angiotensin II. The infrared and Raman spectra of this compound were recorded and discussed assisted with density functional theory using the 6‐31G** basis set and animated pictures. Irbesartan exists in two tautomeric forms which can be isolated in the solid state. The vibrational study has been recorded using a mixture of both forms. ¹³C, ¹⁵N and ¹H NMR theoretical studies have been performed and compared with previously reported experimental data. Theoretical calculations allowed the determination of the main features of the A and B tautomers of Irbesartan both in the vibrational studies and in the NMR spectroscopy. Copyright © 2009 John Wiley & Sons, Ltd.     

不同地理居群大蒜FTIR图谱比较研究

为了比较不同地理居群大蒜的理化性质差异,以25份不同地理居群的大蒜为研究对象,采用傅里叶变换红外光谱仪获取各样品的FTIR图谱,利用光谱仪随机软件中的"快速比较"功能进行了不同地理居群大蒜的相似度比较.结果发现,不同地理居群大蒜的FTIR图谱存在差异,快速比较显示其相似度为76.3%～99.8%,呈现出较为明显的多样性...     

Spatial filtering of side-shift interferograms for two-exposure recording of a gabor hologram. I

The conditions under which side-shift interferograms are formed are analyzed: they are characterized by spherical aberration of the control wave front of converging, quasi-spherical shape, when performing three-dimensional filtering of the diffraction field at the stage of reconstruction of a two-exposure, Gabor hologram. Tomsk State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 98–105, December, 1998.     

Least square fitting of low resolution gamma ray spectra with cubic B-spline basis functions

In this paper, the least square fitting method with the cubic B-spline basis lunctions is derived to reduce the influence of statistical fluctuations in the gamma ray spectra. The derived procedure is simple and automatic. The results show that this method is better than the convolution method with a sufficient reduction of statistical fluctuation.     

Masking of short stimuli by noises with spiked spectra: I. Compressive nonlinearity of cochlea and evaluation of frequency resolution

A psychoacoustic method for measuring masking thresholds based on the application of single-type stimuli and maskers intended for revealing compressive nonlinearity of displacements of the cochlea basila membrane and evaluation of the frequency resolution of hearing in a narrow frequency range near the central frequency of the stimulus is considered. High-frequency pulses with an envelope in the form of a Gaussian function with a sinusoidal filling with the frequency band corresponding to the width of the critical hearing band have been used as stimuli (referred to as compact). Noises with a spike structure of the amplitude spectrum with a limited frequency band width served as maskers. With the central frequencies of stimuli and maskers being equal, a band noise with the central frequency corresponding with a spike of an indented spectrum was called an on_(rip)-frequency masker, while that with the central frequency corresponding to a dip in an indented spectrum was called an off_(rip)-frequency masker. The central frequencies and frequency bands of the stimuli and maskers were 4 kHz and 1000 Hz, respectively. The spike (dip) frequencies of an indented amplitude spectrum of a masker were 1000 Hz. In the case of successive and simultaneous masking, the dependences of the thresholds of off_(rip)-frequency masking of compact stimuli on the masker level revealed compressive nonlinearity of basila membrane displacements. However, threshold on_(rip)/off_(rip)-frequency masking differences visualized it much better. The estimates of the frequency resolution obtained under conditions of simultaneous masking of compact stimuli during variations in the frequency of spikes of indented masker spectra of low and medium levels corresponded to the width of the critical hearing band measured using a classical method of tone masking by a pair of narrow-band noise maskers. Within the spike frequency range of 500–2000 Hz, the steepness of the dependence of off_(rip)-masking of compact stimuli on the spike frequency decreased with an increase in masker levels that pointed to an effect of compressive properties of basila membrane displacements on this parameter.     

Least square fitting of low resolution gamma ray spectra with cubic B-spline basis functions

In this paper,the least square fitting method with the cubic B-spline basis hmctioas is derived to reduce the influence of statistical fluctuations in the gamma ray spectra.The derived procedure is simple and automatic.The results show that this method is better than the convolution method with a sufficient reduction of statistical fluctuation.     

COnstrained Data Extrapolation (CODE): A new approach for high definition vascular imaging from low resolution data

PurposeTo introduce a new approach to reconstruct high definition vascular images using COnstrained Data Extrapolation (CODE) and evaluate its capability in estimating vessel area and stenosis.Materials and methodsCODE is based on the constraint that the full width half maximum of a vessel can be accurately estimated and, since it represents the best estimate for the width of the object, higher k-space data can be generated from this information. To demonstrate the potential of extracting high definition vessel edges using low resolution data, both simulated and human data were analyzed to better visualize the vessels and to quantify both area and stenosis measurements. The results from CODE using one-fourth of the fully sampled k-space data were compared with a compressed sensing (CS) reconstruction approach using the same total amount of data but spread out between the center of k-space and the outer portions of the original k-space to accelerate data acquisition by a factor of four.ResultsFor a sufficiently high signal-to-noise ratio (SNR) such as 16 (8), we found that objects as small as 3 voxels in the 25% under-sampled data (6 voxels when zero-filled) could be used for CODE and CS and provide an estimate of area with an error < 5% (10%). For estimating up to a 70% stenosis with an SNR of 4, CODE was found to be more robust to noise than CS having a smaller variance albeit a larger bias. Reconstruction times were > 200 (30) times faster for CODE compared to CS in the simulated (human) data.ConclusionCODE was capable of producing sharp sub-voxel edges and accurately estimating stenosis to within 5% for clinically relevant studies of vessels with a width of at least 3 pixels in the low resolution images.     

徐州地区胆结石的溶剂萃取的FTIR研究

胆石病是徐州地区的多发病之一,针对徐州地区临床术中取出的五类胆结石利用系列溶剂萃取,用傅里叶变换红外光谱(FTIR)分别表征萃取前后的成分、结构及形态变化。结果表明:所取的五类徐州地区胆结石分别为胆固醇型、难溶物分别为胆红素盐、蛋白质的胆固醇为主的混合型、棕色色素型和黑色色素型胆结石。蛋白质为胆结石的形成提供沉淀基质,对于胆结石成核具有重要意义;胆结石难溶物中胆固醇和羟基碳酸磷灰石相伴而生,羟基磷灰石与胆固醇存在相互作用,促使其结晶析出,从而加速胆结石的形成。结果可以为胆结石的临床诊断、治疗及预防提供一定的参考。     

FTIR光谱高温气体浓度反演方法及残差结构分析

从理论和实验两方面分析了光谱线线宽随温度的变化规律.将HITRAN数据库中常温下的线强参数修正到了测量温度,进而得到合成校准光谱.将合成校准光谱和实验测得的光谱进行非线性最小二乘拟合,得到了不同温度下标准气体CO浓度.这种反演算法的浓度误差在常温下不超过5%,具有很高的精度,但随温度升高浓度误差逐渐增大.从残差光谱曲线...     

The rotational-vibrational spectra of HNCS and DNCS : An analysis of the high resolution spectra

Ro-vibrational spectra of HNCS and DNCS have been obtained in the spectral range 300–4000 cm⁻¹ with a practical resolution limit of 0.06 cm⁻¹ in the region 350–1200 cm⁻¹ and 0.15 cm⁻¹ in the region 1200–4000 cm⁻¹. The observed fine structure permitted definitive assignments for some of the ^PQ_K, ^QQ_K, and ^RQ_K branches in both molecules, and yielded sets of rotational constants in substantial agreement with those obtained from recent microwave and far-infrared studies. Precise estimates of the band origins have been obtained and there is evidence of second-order Coriolis coupling between the three bending modes in each molecule. The isolation of the out-of-plane bending modes has lead to a re-assignment of ν₃, ν₄, ν₅, and ν₆ for each molecule. The band origins, uncorrected for Coriolis interaction, are for HNCS and DNCS, respectively. v₁:3538.6 ±0.3, 2644.5±0.5cm⁻¹;v₂:1989.0 ±0.3, 1944.3±0.5cm⁻¹;v₃:857.0 ±0.6, 851.0±0.1cm⁻¹;v₄:615.0 ±0.5, 549.1±0.2cm⁻¹;v₅:469.2 ±0.1, 365.8 ±0.2cm⁻¹;v₆:539.2 ±0.5, 481.0±0.1cm⁻¹;     

FTIR investigation of organic discharge in polluted water: I. Renex monitoring study

Aliquots of waste water from power stations were analyzed by a special procedure in order to put in evidence the presence of renex, a nonionic detergent. The investigations were performed spectroscopically by FTIR technique. Qualitative and quantitative features of the procedure were established as specific peaks, detection limit and method sensibility. The validity of Lambert-Beer law was checked. Taking into account the selectivity of the method it results the necessity of separating renex from nitrogenous bases in the analyzed water.     

Oscillator strengths for electronic spectra of conjugated molecules from transition gradients. I

Oscillator strengths for ethylene and benzene are calculated from transition gradients in the molecular orbital approximation with zero differential overlap. The results are much closer to the experimental values than the oscillator strengths calculated from transition moments. The effect of inclusion of overlap and other effects are also investigated.     

I.R. Lattice-vibration spectra of MnF2

The room temperature reflectivity of MnF₂ has been measured in the far i.r. between 50 and 800 cm^?1. The reflectivity spectra show four i.r.-active modes which can be identified as E_u and A_2u modes. The spectra also show structure which might be related to multiphonon effects. The dielectric functions were determined by fitting the reflectivity data with classical oscillator parameters.     

High resolutionLMM Auger spectra of low energy from solid surfaces

LMM Auger spectra of Cl, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, and Zn have been investigated with an electrostatic cylindrical spectrometer with energy resolution of about 0.05% in the energy range of 100 eV–1 keV. The Auger electrons have been excited by 5 keV electron bombardment at a grazing incidence angle and the peak of elastically scattered primary electrons have been used for calibration. The line assignments have been discussed.     

Retrieval of ozone vertical column amounts from ground-based high resolution infrared solar spectra

Good infrared spectral regions to retrieve accurately the vertical column amount of ozone from ground observations are proposed. Their selection was based on studies of the influence of spectroscopic (frequencies, halfwidths, intensities) as well as geophysical parameters (volume mixing ratios, temperature profiles) with a particular attention for temperature. The results, obtained in three different spectral regions, with a realistic Tprofile are very consistent.