Electron affinity spectrum of ferrous ion in aqueous solution

Abstract

The study of the absorption spectra of ions in aqueous solution, in relation to the photochemical processes taking place, has up to the present been concerned mainly with anions. The spectra of some of these have been interpreted as electron affinity spectra, according to the views of Franck and Haber. For example, for the I^- ion the elementary process, corresponding to the long wave-length limit of the continuous absorption spectrum in aqueous solution, is represented as I^- HOH + hv → I + H + OH^-. An electron is transferred from the negative ion of the water molecules in its hydration shell. It is not possible to predict on theoretical grounds alone whether a similar process may also occur in the case of cations. In a recent note, however, one of us has shown that be irradiating a solution of FeSO₄ with ultra-violet radiation an appreciable amount of gaseous hydrogen is evolved, with the simultaneous formation of Fe⁺⁺⁺ ion. This was explained by assuming that a primary process analogous to that of the electorn affinity spectrum occurs, viz.., Fe⁺⁺⁺ HOH + hv = Fe⁺⁺⁺ + H + OH^-.