Addendum: A Conjecture on Electron Binding in Aqueous Solutions

Abstract

Experimental evidence for the existence of two forms of reducing species in the radiation chemistry of aqueous solutions has accumulated from kinetic studies (1). Similar conclusions were derived from the investigation of the photochemistry of the halide ions in aqueous solutions (2). Kinetic salt effects (3) yielded evidence that the reducing radical produced in the radiolysis of neutral aqueous solutions is characterized by a negative charge. Platzman has suggested (4) that formation of solvated electrons in irradiated aqueous solutions is feasible. Similar arguments have been presented by Stein (5) and by Weiss (6). Recently Hart and Boag demonstrated in a classic experiment (7) that when pure deaerated water is irradiated by a pulse of 1.8-Mev electrons a transient absorption spectrum characterized by a peak at about 7000 A is observed, which they assigned to the solvated electron. This assignment was confirmed by kinetic studies (8) with the pulsed radiolysis method. Similar transient spectra were observed in H20-NH3 solutions (7) and in aliphatic alcohols.2 The direct observation of the absorption spectrum of the solvated electron raises some interesting questions concerning the charge distribution and energy levels of this hydrated electron. These problems will be considered in the present work.