傅立葉紅外光譜介紹

1、電磁波Gamma RayX-RayUVInfraredMicro WaveShort WaveRadio WavesEnergy eVWavenumber cm-1Wavelength mVisible光與分子的作用光與分子的作用分子激發(fā)產(chǎn)生振動(dòng)振動(dòng)的種類振動(dòng)的種類?伸縮振動(dòng)伸縮振動(dòng)對稱伸縮振動(dòng)不對稱伸縮振動(dòng)例如例如: 水水變形振動(dòng)變形振動(dòng)水的紅外圖15002000250030003500wavenumber cm-16065707580859095100Transmission %正己烷50多不同的振動(dòng)正己烷1000150020002500300035004000wavenumber cm-

2、120406080100Transmission %C-H stretchC-H deformation指紋區(qū)“如何得到一張圖如何得到一張圖傅立葉變換紅外光譜儀傅立葉變換紅外光譜儀傅利葉變換紅外光譜儀原理光源動(dòng)鏡定鏡x分束器LL + xx=0sourceDetectorfixedmirror M1xBeam splitterLx=0例 1: x =0, 相長干涉結(jié)果1. Beam part (定鏡)2. Beam part (動(dòng)鏡)sourceDetectorfixedmirror M1xBeam splitterLx=1/2例 2: x =1/2, 相消性干涉0結(jié)果1. Beam part

3、(定鏡)2. Beam part (動(dòng)鏡)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監(jiān)測器信號監(jiān)測器信號FrequenceIntensity光源光源單色光源單色光源的調(diào)制信號Entstehung des InterferogrammsMirror motionIntensityResulting detector signalFrequenceIntensity9條單一頻率的光源條單一頻率的光源Mirror motionIntensity總和總和:檢測器信號檢測器信號FrequencyIntensity紅外光源紅外光源 X, moving mirrorIntensity干涉圖的來源透射光譜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透射光譜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、光譜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. 鑒定未知物2. 核對已知物定量分析 光譜評價(jià)未知物的鑒定a) 通過光譜解析推出分子結(jié)構(gòu)5001,0001,5002,

10、0002,5003,0003,5004,000Wavenumber / cm-1406080100Transmission %20不同有幾類分子的紅外吸收 烷烴烯烴芳香烴內(nèi)酯鹵化物羧酸鹽酸酐b.) 與標(biāo)準(zhǔn)譜庫比較e.g. by using OPUS/Search未知物的鑒定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驗(yàn)證已知物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