IR SPECTROSCOPY
Infrared Spectroscopy is the type of spectroscopy which is concerned with the study of infrared region of electromagnetic spectrum, which results in vibrational transitions. So it is also called as Vibrational spectroscopy.
The infrared region of the electromagnetic spectrum is divided into three regions; the near-, mid- and far- infrared region. Wavelength of near infrared region is approximately 10-400 cm−1, lying adjacent to the microwave region. Wavelength of middle IR region is 400-4000 cm−1. Wavelength of higher energy near-IR region is approximately 4000–14000 cm−1.
In the context of infrared spectroscopy, wavelength is measured in "wave numbers", which have the unit cm-1. Wave number is the number of waves per cm, which can be calculated from the wavelength.
Wave number = 1 / Wavelength in centimeters
Theory and Principle
In any molecule, atoms or group of atoms are connected by bonds. Photon energies associated with infrared region are not large enough to excite electrons but may induce vibrational excitations of covalently bonded atoms or groups. These covalent bonds are not rigid, but they are analogous to springs which are stretched or bent.
Every bond or a portion of a molecule or a functional group requires different frequency for absorption. Hence, a characteristic peak is observed for every functional group or a part of a molecule.
Criteria for a compound to absorb IR radiation are the change in dipole moment, and applied IR frequency should be equal to the natural frequency of radiation. Otherwise the compound will not give IR peaks.
FIND MORE :-
| Types of Vibrations | Instrumentation |
| Sample Preparation | Fourier Transform |
| Isotope Effect | Applications |
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