Fourier transformation and light dispersion for spectra analysis

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Discussion Overview

The discussion revolves around the use of Fourier transformation in IR and NIR spectroscopy compared to the use of gratings in UV and Vis spectroscopy for light dispersion. Participants explore the concept of a cutoff wavelength and the interchangeability of these techniques in spectral analysis.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that IR and NIR spectroscopy typically use Fourier transformation, while UV and Vis spectroscopy generally employ gratings for light dispersion.
  • Another participant questions the existence of an inherent cutoff frequency in FTIR spectroscopy, suggesting that the spectral response is influenced by factors such as the source, beamsplitter, and detector.
  • A participant seeks clarification on whether the two techniques (Fourier transformation and gratings) can be interchanged for light dispersion.
  • It is mentioned that a linked resource provides an explanation regarding the lower wavelength limit in FTIR machines.

Areas of Agreement / Disagreement

Participants express differing views on the existence of a cutoff wavelength in FTIR spectroscopy, and there is no consensus on the interchangeability of the techniques discussed.

Contextual Notes

The discussion does not resolve the assumptions regarding the definitions of cutoff wavelength or the specific conditions under which the techniques may be interchangeable.

xhtp2000
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IR and NIR spectroscopy usually employ Fourier transformation to separate the signal into individual wavelength, UV and Vis spectroscopy normally apply gratings for light dispersion (into individual wavelength). What is the cutoff wavelength, and why is so?
 
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Are you referring to FTIR spectroscopy?
 
I don't think there is any inherent cutoff frequency when dealing with FTIR spectroscopy. Normally your spectral response will be determined by; A) your source. sometimes a tungsten globar or similar; B) your beamsplitter; C) your detector.


there is a lot of pertinent information here
 
Andy Resnick said:
Are you referring to FTIR spectroscopy?

Yes, for instance, FTIR uses Fourier transformation to convert the signal into individual wavelength, but Vis spectroscopy, like laser-induced breakdown spectroscopy, uses gratings to disperse the light into individual wavelength, I want to know if I can interchange this two techniques for light dispersion .
 
xhtp2000 said:
Yes, for instance, FTIR uses Fourier transformation to convert the signal into individual wavelength, but Vis spectroscopy, like laser-induced breakdown spectroscopy, uses gratings to disperse the light into individual wavelength, I want to know if I can interchange this two techniques for light dispersion .

Christopher.s' link has a nice explanation of the lower wavelength limit in FTIR machines.
 

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