Deuterium isotope effects in the photochemical evolution of hydrogen from aqueous ferrous solutions

The dependence of the isotope separation factor in the photochemical evolution of hydrogen from aqueous solutions of ferrous sulfate on the concentration of H⁺, ferrous, and ferric ions and on the concentration of an organic scavenger (methanol) was investigated. The results are interpreted in terms of a consecutive mechanism involving isotope separation in each of two steps. The respective separation factors in the first step (leading to H atom formation) and in the second (involving oxidation of Fe²⁺ by H) are derived. Isotope effects in radiation and photochemistry are compared. The isotope separation factors obtained support the intermediate hydride formation mechanism for the oxidation of Fe²⁺ by H atoms.