Cage effects and scavenging mechanisms in the photochemistry of the iodide ion in aqueous solutions

Scavenging mechanisms in the photochemistry of the iodide ion were investigated. The nature of the scavenged species is discussed. An iodine atom-electron pair is formed from the primary excited state. H⁺ ions promote specifically the formation of H atoms from these electrons. H⁺ ion and aliphatic alcohols were employed as scavengers for the H atoms. At high scavenger concentration a limiting quantum yield of 0.290 ± 0.005 was observed at 25° and 2537 Å. independent of the nature of the scavenger. Application of specific scavengers made discrimination possible between H atoms and their precursors formed from the dissociation of the excited state of the ion. The dependence of the quantum yield on the scavenger concentration was found to be in agreement with general scavenging equations.