The Effect of Intermittent Light on a Chain Reaction with Bimolecular and Unimolecular Chain-Breaking Steps

Abstract

The effect of intermittent light, as produced by a rotating sector, has been considered for a chain reaction having the following mechanism: $$\begin{array}{c}{\mathrm{A}}_2\text{+hν→2}\mathrm{A},\\ \mathrm{A}+\mathrm{B}\to \mathrm{C}+\mathrm{A},\\ 2\mathrm{A}\to \mathrm{stable\; products},\\ \mathrm{A}\to \mathrm{stable\; products.}\end{array}$$ It has been shown how to calculate the reaction rate as a function of the sector speed for different values of a certain parameter which depends on the individual rate constants and the light intensity and gives, essentially, the relative importance of the bimolecular and unimolecular chain‐breaking steps. The relationships have been exhibited graphically for the case in which one‐fourth of the sector passes the light beam. These relationships may be reversed, making it possible to obtain the rate constants of the intermediate reactions from measurements with intermittent light.