Phosphorescence, Fluorescence, and Chemical Reaction¹

Abstract

ONE of the most important theories brought forward during recent years is that known as the radiation hypothesis, which was developed independently by Perrin and by W. C. McC. Lewis. Briefly stated in an elementary way, this theory postulated that molecules in general have no chemical reactivity, and that they become reactive after they have absorbed energy. In order that a specific reactivity be induced, a definite quantity of energy must be supplied to bring each molecule from its initial stage to its reactive state, this quantity being called the critical increment of energy characteristic of the specific reaction.