傅立叶红外光谱介绍

1、电磁波Gamma RayX-RayUVInfraredMicro WaveShort WaveRadio WavesEnergy eVWavenumber cm-1Wavelength mVisible光与分子的作用光与分子的作用分子激发产生振动振动的种类振动的种类?伸缩振动伸缩振动对称伸缩振动不对称伸缩振动例如例如: 水水变形振动变形振动水的红外图15002000250030003500wavenumber cm-16065707580859095100Transmission %正己烷50多不同的振动正己烷1000150020002500300035004000wavenumber cm-

2、120406080100Transmission %C-H stretchC-H deformation指纹区“如何得到一张图如何得到一张图傅立叶变换红外光谱仪傅立叶变换红外光谱仪傅利叶变换红外光谱仪原理光源动镜定镜x分束器LL + xx=0sourceDetectorfixedmirror M1xBeam splitterLx=0例 1: x =0, 相长干涉结果1. Beam part (定镜)2. Beam part (动镜)sourceDetectorfixedmirror M1xBeam splitterLx=1/2例 2: x =1/2, 相消性干涉0结果1. Beam part

3、(定镜)2. Beam part (动镜)sourceDetectorfixedmirror M1xBeam splitterLexample 3: x = , constructive Interference0Resulting signal1. Beam part (fixed)2. Beam part (movable)x=sourceDetectorfixedmirror M1xBeam splitterLx=3/2example 4: x =3/2, destructive Interference0Resulting signal1. Beam part (fixed)2. Be

4、am part (movable)Mirror motionIntensity监测器信号监测器信号FrequenceIntensity光源光源单色光源单色光源的调制信号Entstehung des InterferogrammsMirror motionIntensityResulting detector signalFrequenceIntensity9条单一频率的光源条单一频率的光源Mirror motionIntensity总和总和:检测器信号检测器信号FrequencyIntensity红外光源红外光源 X, moving mirrorIntensity干涉图的来源透射光谱1.) I

5、n the empty sample compartment an Interferogram is detected. The result of the FOURIER transformation is R().5001000150020002500300035004000wavenumber cm-10.100.200.300.40Single channel intensity X, moving mirrorDetector intensity2.) A second interferogram is detected with the sample placed in the s

6、ample compartment. The result of the FOURIER transformation is S(). S() shows similarities to the reference spectrum R(v), but has lower intensities at the regions the sample absorbs radiation.5001000150020002500300035004000wavenumber cm-10.100.200.300.40Single channel intensity X, moving mirrorDete

7、ctor intensity透射光谱The transmission spectrum T() is calculated as the ratio of the sample and reference single channel spectra: T() = S()/R().5001000150020002500300035004000wavenumber cm-10.100.200.300.40Single channel intensity5001000150020002500300035004000wavenumber cm-1406080100Transmission %20透射

8、光谱Absorbance Transmission - Why?100020003000400050006000Wavenumber cm-1020406080100Transmittance %100020003000400050006000Wavenumber cm-10.00.20.40.60.81.0Absorbance UnitsTransmissionAbsorbanceT() = S()/R()Lambert-Beers law:AB = -log (S()/R()AB = c bPrinciple layout of FT-IR spectrometerSourceMoving

9、mirrorFixed mirrorxBeamsplitterLL + xx=0Layout of an FT-IR spectrometer (TENSOR series)ElectronicSource compartmentSample compartmentSample position Detector Interferometer compartmentAperture wheelFilter wheelEvaluation of IR spectra定性分析：1. 鉴定未知物2. 核对已知物定量分析 光谱评价未知物的鉴定a) 通过光谱解析推出分子结构5001,0001,5002,

10、0002,5003,0003,5004,000Wavenumber / cm-1406080100Transmission %20不同有几类分子的红外吸收 烷烃烯烃芳香烃内酯卤化物羧酸盐酸酐b.) 与标准谱库比较e.g. by using OPUS/Search未知物的鉴定identical material = identical IR spectrum- What you have: sample- What you need:reference library- What you do:comparison with reference library- What you get:ide

11、ntification验证已知物2.) Calculate average spectrum & threshold values3.) Library structure & validation1.) Measure reference sampleWavenumber / cm-1AbsorbanceWavenumber / cm-1AbsorbanceReference library structure Identified sample: material X1.) Measure new samples2.) Compare with libraryIdentif

12、ying new samples3.) Identify material - What you have: sample- What you need:calibration set- What you do:comparison with calibration set- What you get:concentration valueThere are two different forms of calibration:Univariate calibration (OPUS)- Correlates just one piece of spectral information (e.

13、g. peak height or peak area) with the reference values of the calibration set.Multivariate calibration (OPUS/QUANT)- Correlates considerably more spectral information - higher degree of precision - reduced chance of errorOPUS/QUANT uses the Partial Least Squares (PLS) Method.XAnalysis1234AbsorbanceConcentrationX1324AbsorbanceWavelengthCalibrationQuantitative evaluation of spectra2.) Build calibration set (Quant Method)3.) Validate calibration set1.) Measure calibration spectraWave