Quantum characterization of electronic levels in molecules

It is now possible to deduce, in more than one way, the number, nature, quantum characterization, and energy order of electronic levels of diatomic molecules. Experimental verification and identification of these levels, based on vibrational structure of the bands are, in several cases, misleading. Rotational structure analysis and isotopic substitution can, however, in general, give a unique answer to this question. This paper gives a few such instances recently met with in our laboratory