Diatomic molecules, characteristic chemical constants

The most detailed spectroscopic investigations have been carried out with diatomic molecules and at the present time the characteristic constants, obtained from vibrational-rotational spectra arc known for more than 250 diatomic molecules. Several of these compounds are not sufficiently stable to exist in the pure state and have only been observed and studied by spectroscopic methods. Such compounds as CH, NH etc are of great interest as they undoubtedly occur as intermediate products in many chemical reactions. 

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