by Tarek Musslimani

Created on: October 12, 2010

Spectroscopy is a branch of chemistry that uses emission and absorption of electromagnetic radiation in order to obtain information about the structure of atoms and molecules.  In addition, electromagnetic radiation can trigger changes in chemical bonds and can induce chemical reactions such as those which occur  in the branch of chemistry that is called photochemistry. 

Spectroscopy is used in all branches of chemistry such as organic and inorganic chemistries.  Mostly spectroscopy is used in the area of physical chemistry such as its use in the area of photophysics and in LASER spectroscopy.  Spectroscopic science is a relatively new area of chemistry that was developed recently with the advent of instrumentation and after the understanding of the nature of light and the electromagnetic radiation in general.

Spectroscopy is such a powerful technique that using it in chemical research can give a lot of useful information.  In most cases, spectroscopy is used to investigate electronic transitions in atoms and molecules.  Chemical changes in atoms and molecules are triggered partly through the administration of electromagnetic radiation.  

Nuclear changes are in most cases not affected by electromagnetic radiation.  Electromagnetic radiation even in its highest frequency can rarely trigger changes in the nucleus of atoms.  Therefore, the nucleus is usually stable to the effect of electromagnetic radiation or at least not so affected as the electrons of the atom and molecule. 

Electromagnetic radiation that is able to trigger electronic transitions in atoms and molecules is located in the ultra-violet region of the light spectrum or UV.  Also shorter wavelengths can trigger electronic transitions in atoms and molecules such as X-ray radiation. Electronic transitions in the UV region are observed for example in the organometallic complexes of transition metals.

UV light is used in photochemistry to induce chemical reactions in organic molecules.  Shorter wavelength than UV can also induce the breaking of chemical bonds in addition to its ability to trigger electronic transitions in atoms and molecules.  For this reason, UV radiation is considered harmful because it can trigger cancer through altering the structure of important molecules in the body such as the DNA molecule. 

X-ray spectroscopy is another powerful spectroscopic technique

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