Over 3000 E-Learning topics / 5000 Articles & Applications
 
   
   
Introduction to IR Spectroscopy

Spectroscopy can be defined as the interaction between matter and light.  Infrared spectroscopy is a very powerful technique which uses electromagnetic radiation in the infrared region for the determination and identification of molecular structure as well as having various quantitative applications within analytical chemistry. (Figure 1)

We do not aim to provide a mechano-quantic description of light and its interaction with atoms, as this is out of the scope of this module.

However, it is important to note that atoms can absorb energy from electromagnetic radiation; this absorbed energy alters the state of the atoms within the molecule.  These changes are usually manifest in alterations to the frequency and amplitude of molecular vibrations, which may be measured and plotted to produce an infrared spectrum.1 - 4

Infrared spectrometers use optical devices for dispersing and focusing electromagnetic radiation of IR frequency which is passed through the sample and any changes in absorbance measured against a reference beam.

There are three well defined IR regions (near, mid and far).  The boundaries between them are not clearly defined and debate still persists, but broadly they are defined as:

  • Near infrared (12820-4000 cm-1): poor in specific absorptions, consists of overtones and combination bands resulting from vibrations in the mid-infrared region of the spectrum.
  • Mid-infrared (4000-400 cm-1): provides structural information for most organic molecules.
  • Far Infrared (400-33 cm-1): has been less investigated than the other two regions; however, it has been used with inorganic molecules

The low energies, typically encountered within the infrared region, are not sufficient to cause electronic transitions; however, they are large enough to cause changes in the frequency and amplitude of molecular vibrations.

electromagnetic spectrum

Figure 1: The electromagnetic spectrum and the infrared region.

loading data
loading data
loading data
loading data
loading data
loading data
loading data
 
 
 
 
 Home | About UsContact Us | SubscribeTerms and Conditions | Advertise | Privacy Policy 

loading data

loading data

loading data

 

loading data


loading data