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Chapter III CHN Analysis, FT IR …..
spectral information of the original radiation. The interferogram is the Fourier
Transform of the spectrum and the task of the computer is to apply the
inverse Fourier Transform.
Interferometric or Fourier Transform spectroscopy makes use of all
the frequencies from the source simultaneously, rather than sequentially as
in scanning instrument. This was first proposed by Fellgett and hence also
called as Fellgett advantage FTS. The Fellgett advantage is an improvement
in signal to noise ratio of (M) 1/2 , where M is the number of resolution
elements desired in the particular spectrum. It is worth noting that the
resolving power of Fourier Transform instrument is constant over the entire
spectrum, whereas, it varies with frequency in the conventional technique
[7]. Fourier transform spectroscopy is providing simultaneous and almost
instantaneous recording of whole spectrum in the magnetic resonance,
microwave and infrared regions. Fourier Transform (FT) spectroscopy is
equally applicable to both emission and absorption spectroscopy.
Figure: 3.4 Schematic diagram of Michelson interferometer.
The FTIR set up has, as noted earlier, design based on Michelson
interferometer, which is having mainly three important components:
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