“…The methods of calculating the relative probabilities of the vibrational transitions of diatomic molecules or the Franck -Condon factors, as well as the difficulties which are encountered under these conditions, have been elucidated in a number of monographs [14,[42][43][44] and journal papers, references to which can be found in [45,46]. Here we shall limit ourselves to a brief review of papers of a theoretical character which have been devoted to the C 2 molecule.…”