Difference Between FTIR and Raman Spectroscopy

Thekey differencebetween FTIR and Raman spectroscopy is thatFTIR technique measures how much light is remaining from the original light from the light source, whereas Raman spectroscopy measures the energy that scatters after being excited by a laser.

FTIR technique and Raman spectroscopy measure the interaction of energy with the bonds in a sample of the desired (unknown) material.

CONTENTS

1.Overview and Key Difference
2.What is FTIR
3.What is Raman Spectroscopy
4.Side by Side Comparison – FTIR vs Raman Spectroscopy in Tabular Form
5.Summary

What is FTIR?

The term FTIR stands forFourier Transform Infrared Spectroscopy. Fourier Transform Infrared spectrometer is the instrument we can use for this analysis. This instrument is important in organic synthesis, polymer science, petrochemical engineering, the pharmaceutical industry, and food analysis. Additionally, FTIR spectrometers are connected tochromatographyfrom which the mechanism of chemical reactions and the presence of unstable substances can be investigated.

FTIR analysis technique is considered the third generationIR spectrometeranalysis technique. The signal to noise ratio of the spectrum given from this technique is significantly higher than the previous generation IR spectrometers. Other important advantages of this technique involve the high accuracy of wavenumber, the short scan time of all frequencies, the wide scan range, and the reduced interference from stray light.

There are several components in an FTIR spectrometer: it contains a source, interferometer, sample compartment, detector, amplifier, A/D converter, and a computer. The source we use can generate the radiation that can pass through the sample and through the interferometer, which can then reach the detector. Thereafter, the signal tends to be amplified and converted into a digital signal by the amplifier and is analog to the digital converter, respectively.

What is Raman Spectroscopy?

Raman spectra or Raman spectrum is an analytical technique that lies on the inelastic scattering of photons in the sample. The inelastic scattering is calledRaman scattering. This technique is very useful in determining the vibrational modes of molecules. Therefore, the Raman scattering effect is helpful in analytical chemistry for providing a structural fingerprint by which we can identify different molecules.

Radiation types we can use in the detection of a Raman spectra include visible, near IR, or near UV range laser beams. However, near X-ray light beams can also be used here. In this process, the laser beam reacts with the molecular vibrations or phonons, resulting in the energy of the laser photons being shifted up or down.

What is the Difference Between FTIR and Raman Spectroscopy?

FTIR and Raman spectroscopy are two forms of analytical techniques. FTIR is Fourier Transform Infrared Spectroscopy while Raman spectroscopy is an analytical technique that lies on the inelastic scattering of photons in the sample. The key difference between FTIR and Raman spectroscopy is that FTIR technique measures how much light is remaining from the original light from the light source, whereas Raman spectroscopy measures the energy that scatters after being excited by a laser.

Below is a summary of the difference between FTIR and Raman spectroscopy in tabular form.

Summary – FTIR vs Raman Spectroscopy

The term FTIR stands for Fourier Transform Infrared Spectroscopy. Raman spectra or Raman spectroscopy is an analytical technique that lies on the inelastic scattering of photons in a sample. The key difference between FTIR and Raman spectroscopy is that FTIR technique measures how much light is remaining from the original light from the light source, whereas Raman spectroscopy measures the energy that scatters after being excited by a laser.

Reference:

1. “How an FTIR Spectrometer Operates.”Chemistry LibreTexts, Libretexts, 3 Dec. 2020,Available here.

Image Courtesy:

1. “Raman energy levels” By Moxfyre, based on work of User:Pavlina2.0 – vectorization of File:Raman energy levels.jpg(CC BY-SA 3.0)via Commons Wikimedia