Estimated Distributions of Electronic Redox Levels in aq/eaq⁻, Haq⁺/Haq and Some Other Systems

A crude estimate of the distributions of occupied and unoccupied electronic levels of the redox systems aq/e aq − (aq: water traps) and H aq − /H aq is made using known optical and thermodynamic data of the species involved. The distribution of unoccupied levels in H aq − /H aq is thought to be rather narrow, while that of the occupied levels is wide. Under these circumstances, the hydrated electron may be expected to react with H aq − via tunneling with a nearly diffusion controlled rate. The reaction of the mobile electron with H aq − is expected to be rather slow because of the low density of unoccupied states of the system H aq − /H aq at the energy level of e mobile − . Similar considerations were applied to the redox systems H aq /H aq − and OH aq /OH aq − . In both cases, the distribution of unoccupied levels is very broad. The polarograms of H and OH which have recently been measured in the 10 −5 s range may be understood in terms of these estimated distribution functions. Ions of high negative redox potentials such as Mg aq 2+ are expected to be more reactive towards mobile than towards hydrated electrons.