Interaction of Vibrational and Electronic Motion in Alkali Halide Molecules

Abstract

A treatment is developed to interpret the observation that in corresponding regions of the ultraviolet the absorption spectra of sodium iodide and potassium iodide show a band system and a continuum, respectively. The former results from a bound excited state in which the form of the electronic wave function changes drastically with internuclear distance. The latter arises because the nuclear motion can no longer be considered adiabatic with respect to electronic motion, so that the noncrossing rule does not apply.