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1、傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍电磁波Gamma RayX-RayUVInfraredMicro WaveShort WaveRadio WavesEnergy eVWavenumber cm-1Wavelength mVisible傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍光与分子的作用光与分子的作用分子激发产生振动傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍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
2、如例如: 水水变形振动变形振动傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍水的红外图15002000250030003500wavenumber cm-16065707580859095100Transmission %傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍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傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍正己烷1000150020002500300035004000wavenumber cm-120406080100Transmission %C-H stretchC-H deforma
3、tion指纹区“傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍红外光谱分为三个范围:15.000 cm-14.000 cm-1400 cm-15 cm-1NIRNIRMIRMIRFIRFIR傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍如何得到一张图如何得到一张图色散型红外光谱仪色散型红外光谱仪傅立叶变换红外光谱仪傅立叶变换红外光谱仪傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍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/N ratio)傅立
4、叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍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傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍sourceDetectorfixedmirror M1xBeam splitterLL + L + x xx=0例 1: x =0, 相长干涉结果1. Beam part (定镜)2. Beam part (动镜)傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍sourceDetectorfixedmirror M1xBeam splitterLL + L + x xx
5、=1/2例 2: x =1/2, 相消性干涉0结果1. Beam part (定镜)2. Beam part (动镜)傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍sourceDetectorfixedmirror M1xBeam splitterLL + L + x xexample 3: x = , constructive Interference0Resulting signal1. Beam part (fixed)2. Beam part (movable)x=傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍sourceDetect
6、orfixedmirror M1xBeam splitterLL + L + x xx=3/2example 4: x =3/2, destructive Interference0Resulting signal1. Beam part (fixed)2. Beam part (movable)傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍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傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Entstehung d
7、es 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:傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍检测器信号检测器信号FrequencyIntensity红外光源红外光源 X, moving mirrorIntensity干涉图的来源傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍透射光谱1.) In the empty sample compa
8、rtment an Interferogram is detected. The result of the FOURIER transformation is R().Fourier-TransformationFourier-Transformation5001000150020002500300035004000wavenumber cm-10.100.200.300.40Single channel intensity X, moving mirrorDetector intensity傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍2.) A second i
9、nterferogram is detected with the sample placed in the sample 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.Fourier-TransformationFourier-Transformation5001000
10、150020002500300035004000wavenumber cm-10.100.200.300.40Single channel intensity X, moving mirrorDetector intensity透射光谱傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍The transmission spectrum T() is calculated as the ratio of the sample and reference single channel spectra: T() = S()/R().50010001500200025003000
11、35004000wavenumber cm-10.100.200.300.40Single channel intensity5001000150020002500300035004000wavenumber cm-1406080100Transmission %20ratioratio透射光谱傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Absorbance Transmission - Why?100020003000400050006000Wavenumber cm-1020406080100Transmittance %10002000300040005000
12、6000Wavenumber cm-10.00.20.40.60.81.0Absorbance UnitsTransmissionAbsorbanceT() = S()/R()Lambert-Beers law:AB = -log (S()/R()AB = c b傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Principle layout of FT-IR spectrometerSourceMovingmirrorFixed mirrorxBeamsplitterLL + xx=0傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Layout
13、 of an FT-IR spectrometer (TENSOR series)ElectronicSource compartmentSample compartmentSample position Detector Interferometer compartmentAperture wheelFilter wheel傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍NIR:Source : tungsten lampOptical material : QuartzDetector: Ge, InGaAsMIR: Source: GlobarOptical ma
14、terial: KBr, ZnSeDetector: DTGS, MCTFIR:Source : Globar, Hg lampOptical material : PE, CsIDetector: DTGS, BolometerDifferences between NIR, MIR, FIROptical components:傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Fourier Transformation (FT)傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Data acquisition results in a digi
15、tized interferogram, I(x), which is converted into a spectrum by means of the mathematical operation called a Fourier Transform (FT).The general equation for the Fourier Transform is applicable to a continuous signal. If the signal (interferogram) is digitized, however, and consists of N discrete, e
16、quidistant points, then the discrete version of the FT (DFT) must be used: S(k . ) = I(n x) exp (i2k n/N)The continuous variables x and have been replaced with n x and k , representing the n discrete interferogram points and the k discrete spectrum points. The fact that we now have a discrete, rathe
17、r than continuous, function, and that it is only calculated for a limited range of n (i.e. the measured interferogram has a finite length) leads to important effects known as the picket-fence effect and leakage.The Fourier Transform傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍sourcedetectormovablemirror M2fi
18、xedmirror M1xBeam splitterLL + xx=0高光谱分辨低光谱分辨傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍添零The picket-fence effect occurs if the interferogram contains frequency components which do not exactly coincide with the data point positions, k. , in the spectrum. The effect can be thought of as viewing the spectrum
19、 through a picket fence, thereby hiding those frequencies that are behind the pickets, i.e. between the data point positions k. . In the worst case, if a frequency component is exactly between two sampling positions, a signal reduction of 36% can occur. The picket-fence effect can be reduced by addi
20、ng zeros to the end of the interferogram (zero filling) before the DFT is performed. This interpolates the spectrum, increasing the number of points per wavenumber. The increased number of frequency sampling positions reduces the error caused by the picket-fence effect. Generally, the original inter
21、ferogram size should always be at least doubled by zero filling, i.e. zero filling factor (ZFF) of two is chosen. Zero-filling interpolates using the instrument line-shape, and in most cases is therefore superior to polynominal or spline interpolation methods that are applied in the spectral domain.
22、1,7961,7981,8001,8021,8041,8061,808Wavenumber, cm-10.350.400.450.500.55Single channel1,7961,7981,8001,8021,8041,8061,808Wavenumber, cm-10.350.400.450.500.55Single channelZero-filling factor 2Zero-filling factor 8傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍截趾函数In a real measurement, the interferogram can onl
23、y be measured for a finite distance of mirror travel. The resulting interferogram can be thought of as an infinite length interferogram multiplied by a boxcar function that is equal to 1 in the range of measurement and 0 elsewhere. This sudden truncation of the interferogram leads to a sinc( ) (i.e.
24、 sin( )/ ) instrumental lineshape. For an infinitely narrow spectral line, the peak shape is shown at the top of the figure on the right. The oscillations around the base of the peak are referred to as “ringing”, or “leakage”.The solution to the leakage problem is to truncate the interferogram less
25、abruptly. This can be achieved by multiplying the interferogram by a function that is 1 at the centerburst and close to 0 at the end of the interferogram. This is called apodization, and the simplest such function is a ramp, or “triangular apodization”. The choice of a particular apodization functio
26、n depends on the objectives of the measurement. If the maximum resolution of 0.61/L is required, then boxcar apodization (i.e no apodization) is used. If a resolution loss of 50% (compared to the maximum resolution of 0.61/L) can be tolerated, the HAPP-GENZEL or, even better, 3-Term BLACKMAN-HARRIS
27、function is recommended.ABOXCAR (no apodization)BTriangularCTrapezoidalDHAPP-GENZELE3-TERM BLACKMAN-HARRIS傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Evaluation of IR spectra傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍定性分析：1. 鉴定未知物2. 核对已知物定量分析 光谱评价傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍未知物的鉴定a) 通过光谱解析推出分子结构5001,0001,5
28、002,0002,5003,0003,5004,000Wavenumber / cm-1406080100Transmission %20傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍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傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍b.) 与标准谱库比较e.g. by using OPUS/Search未知物的鉴定傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍identical material = identical IR spectrum- What yo
29、u have: sample- What you need:reference library- What you do:comparison with reference library- What you get:identification验证已知物傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍2.) Calculate average spectrum & threshold values3.) Library structure & validation1.) Measure reference sampleWavenumber / cm-1Absorban
30、ceWavenumber / cm-1AbsorbanceReference library structure傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍 Identified sample: material X1.) Measure new samples2.) Compare with libraryIdentifying new samples3.) Identify material 傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍- What you have: sample- What you need:calibration
31、 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.g. peak height or peak area) with the reference values of the calibration set.Multivaria
32、te 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 spectra傅立叶红外光
33、谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍2.) Build calibration set (Quant Method)3.) Validate calibration set1.) Measure calibration spectraWavenumber / cm-1AbsorbanceSetup of a Quant Method1234AbsorbanceConcentration傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍 Concentration:58 vol. %1.) Measure sample2.) Compare with
34、 calibration setDetermine quantitative results (e.g. concentration values)3.) Result 傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍FT-IR measurements傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Enter sample nameStart the background and sample measurement傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立
35、叶红外光谱介绍Sampling bandwidth in interferogram domain傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍The FT of a measured interferogram yields a complex spectrum. The aim of the phase correction is to calculate the real spectrum.Interpolation of the spectrum by adding zeros to the end of the interferogram傅立叶红外光谱介绍傅
36、立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Defines the separation of adjacent peaks傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍Acquisition modesingle sideddouble sidedfast backwardforward and backward傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍傅立叶红外光谱介绍If you have any further questions about IR spectroscopy, please contact the application t
37、eam of Bruker Optics:Europe:Bruker Optik GmbHRudolf-Plank-Str. 2776275 Ettlingen, GermanyPhone: +49 7243 504 600Fax: +49 7243 504 698infobrukeroptics.deNorth America:Bruker Optics Inc19 Fortune DriveBillerica, MA 01821, USAPhone: +1 978 439 9899Fax: +1 978 663 Asia:Bruker Optik Asia Pacific Ltd.Unit 601, 6/F, Tower 1Enterprise SquareNo. 9, Sheung Yuet Road, Hong KongPhone: +852 27966100Fax: +852
