‘Condon Parabolæ’ in Molecular Spectra

Abstract

IN his original paper on the quantitative explanation of the Franck–Condon principle, Condon¹ predicted the expected locus of strong bands on the v′, v″ plane by classical mechanics and the correspondence principle. For simple harmonic oscillator potentials he predicted a quadratic relationship between v′ and v″ which can be compared with the position of observed strong bands on the Deslandres diagram. The well-known primary Condon ‘parabolæ’ which often pass through (0,0) and are roughly symmetric about v′ = v″ were thus confirmed.