Electrochromism (stark effect) in solids due to isolated absorbing centers

Abstract

A study has been made of the effect of applied electric fields upon the absorption spectrum of a dye molecule (methyl red) dissolved in a relatively inert, transparent, matrix of high dielectric strength (polystyrene). Theory indicates that the existence of a large dipole moment in either ground or excited state (or in both, if the moment differs in the two states) should lead to a broadening of the absorption band. In contrast, excited states of appropriate type lying close to that involved in the transition should produce a shift to the red. In the present instance the second shift dominates, and one observes, with a field of about one million v/cm, a shift of around 10 Å of the principal band which is centered near 5000 Å. Possible uses of this technique are in evaluating the local field at an absorbing molecule and in estimating dipole moments of various states.