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It is shown that the energy of electronic minority charge carriers injected into an electrolyte from an illuminated semiconductor electrode may be significantly greater than that predicted by previous models. The time constants for tunneling from the semiconductor states in the depletion region are evaluated by two methods: approximating the final states as a continuum resulting from strong electron-vibration interaction in the electrolyte, and calculating the oscillation time between semiconductor states and the discrete electrolyte states before vibrational relaxation. Comparisons are made with the time constants for intraband electronic relaxation in the semiconductor, including the effects of quantization due to confinement in the depletion region, and with those for the vibrational relaxation in the electrolyte. The general conditions for the injection of hot carriers from semiconductors into electrolytes are specified.

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The valence effective Hamiltonian technique (VEH), and modified neglect of differential overlap (MNDO) calculations are used to study the influence of strain induced by side chains on the geometry of polydiacetylene backbones and the resulting polymer band structure, band gap, and ionization potential. Simulations of strain effects on the polymer backbone yield variations in optical properties which are similar to those observed experimentally during thermochromic phase changes in urethane-substituted polydiacetylenes. Our results suggest that these changes in optical properties are related to strain at points of substituent attachment and not to fundamental changes in the backbone geometry such as an acetylenic-to-butatrienic transformation.

The electron transfer process, which occurs during oxygen evolution at Pt electrodes from water molecules in the double layer, is analyzed. The process proceeds by electron tunneling through an insulating anodic Pt oxide film to the underlying Pt metal as oxygen is evolved. The rate equation for the reaction is based on a model of quantum tunneling through a barrier which is a composite of both the oxide film and the inner Helmholtz layer. For a barrier thickness of i0 A, the probability of tunneling decreases by a factor of three as the electrode potential increases from 1.29 to 2.01 V vs. RHE. This decrease is small when compared to the observed, ca. 10 ~, increase in current density for the same potential span. The current density is controlled primarily by the distribution of electron energy states of the reacting donor species which are water molecules in the inner Helmholtz plane. At a constant potential, the tunneling probability depends exponentially on the thickness of the potential barrier, and therefore the rate of the oxygen evolution reaction is strongly dependent on the Pt oxide film thickness.