Isotope effects on vibrational transition probabilities. II. Electronic transitions of isotopic nitrogen, nitric oxide, and oxygen molecules

Franck-Condon factors are given for the major electronic transitions of the normal and stable-isotope-labeled molecules N₂, NO, and O ₂, for vibrational levels up to 10 of the v″ = 0 and v″ = 0 progressions and for the (1, 1) transition. Appreciable isotope effects on vibrational transition probabilities are found in the O₂ Schumann-Runge and Herzberg bands, in the O₂⁺ second negative bands, in the NO beta and "M" bands, and in the N₂ Vegard-Kaplan bands. The magnitude of isotope effects on Franck-Condon factors is determined by differences in reduced masses between two isotopic molecules, as well as by differences in equilibrium internuclear distances between the two electronic states involved. The ratio of Franck-Condon factors of the light and heavy molecules decreases in the v″ = 0 and v′ = 0 progressions with increasing quantum number. The isotope effect on r centroids is very small.