布鲁克红外光谱培训-50页PPT精品文档

6593.0
6592.5
6592.0
低光谱分辨
detector
0.5
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.Δ~ , in the spectrum. The effect can be thought of as viewing the spectrum through a picket fence, thereby hiding those frequencies that are behind the pickets, i.e. between the data point positions k.Δ~ . 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 adding 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 interferogram 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.
Source: Globar Optical material: KBr, ZnSe Detector: DTGS, MCT
Source : Globar, Hg lamp Optical material : PE, CsI Detector: DTGS, Bolometer
傅立叶红外光谱介绍
Fourier Transformation (FT)
Aperture wheel Filter wheel
Sample position
Interferometer compartment
傅立叶红外光谱介绍
Differences between NIR, MIR, FIR
Optical components:
NIR: MIR: FIR:
Source : tungsten lamp Optical material : Quartz Detector: Ge, InGaAs
Detector intensity
X, moving mirror
Fourier-Transformation
Single channel intensity 0.10 0.20 0.30 0.40
4000 3500 3000 2500 2000 1500 1000 500 wavenumber cm-1
傅立叶红外光谱介绍
The Fourier Transform
Data acquisition results in a digitized interferogram, I(x), which is converted into a spectrum by means of the mathematical operation called a Fourier Transform (FT).
傅立叶红外光谱介绍
振动的种类? 例如: 水
伸缩振动
变形振动
对称伸缩振动
不对称伸缩振动
傅立叶红外光谱介绍
Transmission [%] 60 65 70 75 80 85 90 95 100
水的红外图
3500
3000
2500 wavenumber cm-1
2000
1500
傅立叶红外光谱介绍
正己烷
傅利叶变换红外光谱仪原理 动镜
x
定镜
L
光源
L + x x=0
分束器
傅立叶红外光谱介绍
例 1: x =0, 相长干涉
1. Beam part (定镜)

2. Beam part (动镜)
结果
fixed mirror M1
x L + x
x=0
L
source
Beam splitter
Detector
傅立叶红外光谱介绍
透射光谱
2.) A second interferogram is detected with the sample placed in the sample compartment. The result of the FOURIER transformation is S(ν). S(ν) shows similarities to the reference spectrum R(v), but has lower intensities at the regions the sample absorbs radiation.
傅立叶红外光谱介绍
高光谱分辨
1.0
0.9
0.8
Single channel
0.5
0.6
0.7
6596.0
6595.5
6595.0
6594.5
6594.0
6593.5
Wavenumber cm-1
6593.0
6592.5
6592.0
1.0
C:\Programme\OPUS5-finalrelease\DATA\Crnin2ob.0
傅立叶红外光谱介绍
例 2: x =1/2, 相消性干涉
1. Beam part (定镜)

2. Beam part (动镜)
结果
fixed mirror M1
x
L + x 0 x=1/2
L
source
Beam splitter
Detector
傅立叶红外光谱介绍
example 3: x = , constructive Interference
Detector intensity
X, moving mirror
Fourier-Transformation
Single channel intensity 0.10 0.20 0.30 0.40
4000 3500 3000 2500 2000 1500 1000 500 wavenumber cm-1
N2O
LP-GAS-CELL
24/01/89
movable mirror M2
x
fixed mirror M1
L
source
L + x x=0
Beam splitter
0.9
0.8
Single channel
0.7
0.6
6596.0
6595.5
6595.0
6594.5
6594.0
6593.5
Wavenumber cm-1
50多不同的振动
傅立叶红外光谱介绍
正己烷
100
80
60
Transmission [%]
40
C-H stretch
C-H deformation
4000
3500
3000
2500
2000
wavenumber cm-1
„指纹区“
1500
1000
20
傅立叶红外光谱介绍
红外光谱分为三个范围:
NIR
15.000 cm-1
0.0
0.2
0.4
0.6
Absorbance
Lambert-Beer‘s law: AB = -log (S(ν)/R(ν)) AB = • c • b
6000
5000
4000
3000
Wavenumber cm-1
2000
1000
20
0
傅立叶红外光谱介绍
Principle layout of FT-IR spectrometer
傅立叶红外光谱介绍
傅立叶红外光谱介绍
电磁波
Energy [eV]
Wavenumber [cm-1]
Wavelength [m]
Visible
Gamma Ray
X-Ray
UV
Infrared
Micro Wave
Short Wave
Radio Waves
傅立叶红外光谱介绍
光与分子的作用
分子激发产生振动
Σ S(k . Δ~ ) = I(n Δx) exp (i2πk n/N)