布鲁克红外光谱培训1Introduction to FT-IR_c

傅立叶红外光谱介绍•张远征•13601358075•01068474806-669•[e-mail]傅立叶红外光谱介绍傅立叶红外光谱介绍电磁波GammaRayX-RayUVInfraredMicroWaveShortWaveRadioWavesEnergy[eV]Wavenumber[cm-1]Wavelength[m]Visible傅立叶红外光谱介绍光与分子的作用分子激发产生振动傅立叶红外光谱介绍振动的种类?伸缩振动对称伸缩振动不对称伸缩振动例如:水变形振动傅立叶红外光谱介绍水的红外图15002000250030003500wavenumbercm-16065707580859095100Transmission[%]傅立叶红外光谱介绍正己烷50多不同的振动傅立叶红外光谱介绍正己烷1000150020002500300035004000wavenumbercm-120406080100Transmission[%]C-HstretchC-Hdeformation„指纹区“傅立叶红外光谱介绍红外光谱分为三个范围:15.000cm-14.000cm-1400cm-15cm-1NIRMIRFIR傅立叶红外光谱介绍如何得到一张图色散型红外光谱仪傅立叶变换红外光谱仪傅立叶红外光谱介绍色散型红外光谱仪DetectorDetector优点:-不需要计算机缺点:-速度慢-光通量低=灵敏度低(S/Nratio)傅立叶红外光谱介绍傅利叶变换红外光谱仪原理光源动镜定镜x分束器LL+xx=0傅立叶红外光谱介绍sourceDetectorfixedmirrorM1xBeamsplitterLL+xx=0例1:x=0,相长干涉结果1.Beampart(定镜)2.Beampart(动镜)傅立叶红外光谱介绍sourceDetectorfixedmirrorM1xBeamsplitterLL+xx=1/2例2:x=1/2,相消性干涉0结果1.Beampart(定镜)2.Beampart(动镜)傅立叶红外光谱介绍sourceDetectorfixedmirrorM1xBeamsplitterLL+xexample3:x=,constructiveInterference0Resultingsignal1.Beampart(fixed)2.Beampart(movable)x=傅立叶红外光谱介绍sourceDetectorfixedmirrorM1xBeamsplitterLL+xx=3/2example4:x=3/2,destructiveInterference0Resultingsignal1.Beampart(fixed)2.Beampart(movable)傅立叶红外光谱介绍Mirrormotion监测器信号Frequence光源单色光源单色光源的调制信号傅立叶红外光谱介绍EntstehungdesInterferogrammsMirrormotionResultingdetectorsignalFrequence9条单一频率的光源Mirrormotion总和:傅立叶红外光谱介绍检测器信号Frequency红外光源X,movingmirror干涉图的来源傅立叶红外光谱介绍透射光谱1.)IntheemptysamplecompartmentanInterferogramisdetected.TheresultoftheFOURIERtransformationisR(ν).Fourier-Transformation5001000150020002500300035004000wavenumbercm-10.100.200.300.40SinglechannelintensityX,movingmirrorDetectorintensity傅立叶红外光谱介绍2.)Asecondinterferogramisdetectedwiththesampleplacedinthesamplecompartment.TheresultoftheFOURIERtransformationisS(ν).S(ν)showssimilaritiestothereferencespectrumR(v),buthaslowerintensitiesattheregionsthesampleabsorbsradiation.Fourier-Transformation5001000150020002500300035004000wavenumbercm-10.100.200.300.40SinglechannelintensityX,movingmirrorDetectorintensity透射光谱傅立叶红外光谱介绍ThetransmissionspectrumT(ν)iscalculatedastheratioofthesampleandreferencesinglechannelspectra:T(ν)=S(ν)/R(ν).5001000150020002500300035004000wavenumbercm-10.100.200.300.40Singlechannelintensity5001000150020002500300035004000wavenumbercm-1406080100Transmission[%]20ratio透射光谱傅立叶红外光谱介绍Absorbance-Transmission-Why?100020003000400050006000Wavenumbercm-1020406080100Transmittance[%]100020003000400050006000Wavenumbercm-10.00.20.40.60.81.0AbsorbanceUnitsTransmissionAbsorbanceT(ν)=S(ν)/R(ν)Lambert-Beer‘slaw:AB=-log(S(ν)/R(ν))AB=•c•b傅立叶红外光谱介绍PrinciplelayoutofFT-IRspectrometerSourceMovingmirrorFixedmirrorxBeamsplitterLL+xx=0傅立叶红外光谱介绍LayoutofanFT-IRspectrometer(TENSORseries)ElectronicSourcecompartmentSamplecompartmentSamplepositionDetectorInterferometercompartmentAperturewheelFilterwheel傅立叶红外光谱介绍NIR:Source:tungstenlampOpticalmaterial:QuartzDetector:Ge,InGaAsMIR:Source:GlobarOpticalmaterial:KBr,ZnSeDetector:DTGS,MCTFIR:Source:Globar,HglampOpticalmaterial:PE,CsIDetector:DTGS,BolometerDifferencesbetweenNIR,MIR,FIROpticalcomponents:傅立叶红外光谱介绍FourierTransformation(FT)傅立叶红外光谱介绍Dataacquisitionresultsinadigitizedinterferogram,I(x),whichisconvertedintoaspectrumbymeansofthemathematicaloperationcalledaFourierTransform(FT).ThegeneralequationfortheFourierTransformisapplicabletoacontinuoussignal.Ifthesignal(interferogram)isdigitized,however,andconsistsofNdiscrete,equidistantpoints,thenthediscreteversionoftheFT(DFT)mustbeused:S(k.Δ)=ΣI(nΔx)exp(i2πkn/N)Thecontinuousvariablesxandhavebeenreplacedwithnxandk,representingthendiscreteinterferogrampointsandthekdiscretespectrumpoints.Thefactthatwenowhaveadiscrete,ratherthancontinuous,function,andthatitisonlycalculatedforalimitedrangeofn(i.e.themeasuredinterferogramhasafinitelength)leadstoimportanteffectsknownasthepicket-fenceeffectandleakage.TheFourierTransform~~~傅立叶红外光谱介绍sourcedetectormovablemirrorM2fixedmirrorM1xBeamsplitterLL+xx=0C:\Programme\OPUS5-finalrelease\DATA\Crnin2ob.0N2OLP-GAS-CELL24/01/896592.06592.56593.06593.56594.06594.56595.06595.56596.0Wavenumbercm-10.50.60.70.80.91.0SinglechannelC:\Programme\OPUS5-finalrelease\DATA\Crnin2ob.0N2OLP-GAS-CELL24/01/896592.06592.56593.06593.56594.06594.56595.06595.56596.0Wavenumbercm-10.50.60.70.80.91.0Singlechannel高光谱分辨低光谱分辨傅立叶红外光谱介绍添零Thepicket-fenceeffectoccursiftheinterferogramcontainsfrequencycomponentswhichdonotexactlycoincidewiththedatapointpositions,k.Δ,inthespectrum.Theeffectcanbethoughtofasviewingthespectrumthroughapicketfence,therebyhidingthosefrequenciesthatarebehindthepickets,i.e.betweenthedatapointpositionsk.Δ.Intheworstcase,ifafrequencycomponentisexactlybetweentwosamplingpositions,asignalreductionof36%canoccur.Thepicket-fenceeffectcanbereducedbyaddingzerostotheendoftheinterferogram(zerofilling)beforetheDFTisperformed.Thisinterpolatesthespectrum,increasingthenumberofpointsperwavenumber.Theincreasednumberoffrequencysamplingpositionsreducestheerrorcausedbythepicket-fenceeffect.Generally,theoriginalinterferogramsizeshouldalwaysbeatleastdoubledby