A study of the mechanism of photochemical electron transfer processes in solution

Abstract

The flash photolysis of halide solutions yields unstable species believed to be the dihalide ion the absorption spectrum of which we have observed and photographed. This transient has been noted during the photolysis of ( а ) the aqueous solutions of KCl, KBr, KI, HCl, NaCl, NaBr, NH 4 C1, MgCl 2 , HgCl 2 , CaCl 2 and SrCl 2 , ( b ) the ethyl and methyl alcoholic solutions of KBr and KI, ( c ) the methyl cyanide solution of KI. The effect of the addition of sulphuric acid, potassium hydroxide and Mn 2+ ion to certain of the solutions has also been studied. Our interpretation of the results of the flash photolysis of KI in solution, based on the Rigg & Weiss mechanism of electron transfer, involves the postulation of the splitting of the solvent molecule. In water solution, this would mean the formation of hydrogen. The production of hydrogen in aqueous solutions of KI of pH 6 to 7 has been confirmed by an investigation of the steady state photolysis.