Some Neglected Subcases of Predissociation in Diatomic Molecules

Abstract

The theoretically to be expected effects of the Franck‐Condon factor in predissociation in diatomic molecules are examined qualitatively for cases in which the potential‐energy curve of the predissociating electronic state crosses that of the predissociated state at an internuclear distance r_c near or less than the equilibrium distance r_e of the latter state. It is shown that the incidence of predissociation as a function of the vibrational and rotational quantum numbers v and J should be quite different in such cases than in the more familiar cases where r_c>r_e. Various subcases of Herzberg's cases a, b, c depending on the relation of r_c to r_e are specified and designated. Some probable examples of known predissociations where r_c<r_e are discussed. The need for further quantitative studies is emphasized.