This document provides an overview of Fourier transform infrared (FTIR) spectroscopy. It begins with background on spectroscopy and how FTIR works. FTIR uses a Michelson interferometer to split infrared light into multiple wavelengths, which interact with and are absorbed by a sample. The detected signal is then converted to an infrared spectrum using a Fourier transform algorithm. This allows FTIR to capture an entire infrared spectrum much faster than a dispersive spectrometer. The document explains the working principles, components, and advantages of FTIR spectroscopy.

2. FTIR Spectroscopy
Presented by:
Abdul Ahad, 20685
Presented To:
Dr. Khalid Mehmood-ur-
Rehman
Riphah International University
Faisalabad

3. Contents
Spectroscopy
Background
Fourier Transform
Working Principle
Michelson Interferometer
Comparison
References

4. Spectroscopy
 Spectroscopy is the
study of the
interaction between
light and matter where
the absorption and
emission of light or
other radiation by the
matter are studied and
measured.

5. Introduction
Initially “Dispersive Spectroscopy” technique was
used .
Monochromatic beam absorbed by sample and then
studied.
The same process was repeated for different
wavelengths.

6. Fourier Transform
 The Fourier Transform is a tool that breaks a waveform into an
alternate representation, characterized by sine and cosines. The
Fourier Transform shows that any waveform can be re-written as
the sum of sinusoidal functions.
 The Fourier Transform converts the detector output to an
interpretable spectrum.

7. Fourier Transform Spectroscopy
 Fourier-transform spectroscopy is a less intuitive way to
obtain the same information. Rather than shining a
monochromatic beam of light at the sample, this technique
shines a beam containing many frequencies of light at once
and measures how much of that beam is absorbed by the
sample. Next, the beam is modified to contain a different
combination of frequencies, giving a second data point. This
process is rapidly repeated many times over a short time
span. Afterwards, a computer takes all this data and works
backward to infer what the absorption is at each wavelength.

8. Schematic Diagram

9. Principle
IR radiation is used.
Beam is splitted by Michelson Interferometer.
Sample is placed just before the Detector.
Infrared Radiation (700nm-1mm) is fallen on the
sample.

10. Conti…
Some of them absorbed and some passed through.
Radiations passing through the sample, form a
spectrum on detector.
This spectrum represent a molecular fingerprint of
sample.
Each chemical structure will produce a unique
fingerprint.

11. Michelson Interferometer

12. Michelson Interferometer

13. The computer that process the data works on
mathematical algorithm “Fourier Transform”.
The interferogram is converted to a spectrum by
Fourier transformation.
The result of Fourier transformation is a spectrum of
the signal at a series of discrete wavelengths.

15. What information can FTIR provide?
It can identify unknown materials.
It can determine the quality of sample.
It can determine the amount of components in a
mixture.

16. Comparison
Dispersive Spectrometer
In order to measure an
IR spectrum, the
Dispersive Spectrometer
takes more time.
The detector receives
only a few % of light.
FR-IR
In order to measure an
IR spectrum, FTIR takes
only a few seconds.
The detector receives
UPTO 50% of energy of
light.

17. References
 https://en.wikipedia.org/wiki/Fourier-transform_infrared_spectroscopy
 https://www.sciencedirect.com/topics/engineering/fourier-transform-infrared-
spectroscopy
 https://www.thermofisher.com/pk/en/home/industrial/spectroscopy-elemental-
isotope-analysis/spectroscopy-elemental-isotope-analysis-learning-
center/molecular-spectroscopy-information/ftir-information/ftir-basics.html
 https://mathworld.wolfram.com/FourierTransform.html