Upload
siva-ok
View
47
Download
4
Embed Size (px)
DESCRIPTION
Spectra of Single Beam(Background and Sample),Transmission factor,Absorbance
Citation preview
5/29/13 Basic FTIR theory(3)─Spectra of Single Beam(Background and Sample),Transmission factor,Absorbance
www.kdijpn.co.jp/English/FTIReprinciple_04.htm 1/2
Portable EDX Analyzer
SKYRAY EDX PocketV
[FTIR Principles]
(1)What is FT-IR?
(2)Interferrence of light waves,
Interferogram spectrum,
Fourier Transform,
and single beam sprctrum
(3)Single Beam Spectrum of
Background and Sample,
Transmission factor spectrum,
Absorbance spectrum
Now under preparation
(4)Beer-Lambert Law and
Absorbance spectrum
Now under preparation
[FTIR related products]
FTIR Gas Analyzer
MIDAC I Series
Openpath FTIR gas analyzer
MIDAC Air Monitoring System
Sample pretreatment device for
solid FTIR or FTIR microscopy
analysis
Basic FTIR theory (3)
Spectra of Single Beam(Background and Sample), Transmission factor, and Absorbance
[Single Beam]
In FT-IR measurement, we generally use the term "Collect Background" or "Collect Samples".
Background means a spectrum of before-cell beams with no IR absorption.
It can be either in interferogam or single beam spectrum, but usually we use single beam spectrum.
[Before and After Sample Cell]
As we have seen, absorption occurs if it pass thorugh an IR active sample. (See the following diagram)
Transmission Factor is defined as Tλ = I'λ/ Iλ
and Absorbance unit = -logT(log is common logarithms)
where I' λis the intensity of light at a specified wavelength λ that has passed through a sample (transmitted light
intensity) and Iλ is the intensity of the light before it enters the sample or incident light intensity (or power).
In the field of FT-IR spectroscopy, Absorbance is mainly used because it complies with Beer-Lambert law of
Absorbance unit = ε* L * C
where ε = Absorption coefficient
L = Optical Cell Path Length
C = Concentration of a sample
In "Basic FTIR Principle (2)", we described, "plotting amplitudes of decomposed waves will form a spectrum over wide-
range wavelength called Single Beam spectrum". Background single beam is a one with no absorption because of being
purged by IR-inactive gas, and sample single beam has IR absorption in some wavenumber region.
The above sample is the one taken under amnbient air and shows shows absorption becase of CO2 and H2O.
In the same way, transmittance spectrum and absorbance spectrum can be get by plotting results at each λ in series.
5/29/13 Basic FTIR theory(3)─Spectra of Single Beam(Background and Sample),Transmission factor,Absorbance
www.kdijpn.co.jp/English/FTIReprinciple_04.htm 2/2
Micro Support's
Micro Sampling Machine
Axis Pro
Pyrolyzer for high pressure or
with catalyst environment
CDS 5200HP pyrolyzer
GC-IR Brill Cell Interface
CDS Analytical'
GC-IR Brill Cell Interface
Can measure pyrolized
compounds with FTIR
[New Items]
NTS International
Geiger-Muler counter radiation
detector
[To a Former Page] [To "Articles Top"] [To Next (Now under preparation)]
Copyright (C) 2011 KDI Co. Ltd. All Rights Reserved.