A model to explain the current-doubling mechanism on Ti02 is advanced. This involves both the interaction of holes and radicals produced by the holes with the Ti02 band levels, oxidizing agents, reducing agents, and the solvent. This model can be used to explain why current doubling is almost never twice the hole current. In individual experiments it was noted that the amount of current doubling is directly dependent on the degree of doping of the crystal which we relate to tunneling effects at the conduction band edge. A large number of organic species were observed to produce current doubling on the Ti02 electrode. In the case of methanol the concentration dependence of this current was used to calculate the relative competition for holes of the solvent as well as the ability of the solvent to react with the radical. That is in preference to the radical injecting an electron into the conduction band. Relative capture cross sections of reducing agents (mostly cerous ion) with respect to the current-doubling organic compounds were measured by titrating one against the other. In a similar manner the quenching effect of oxidizing agents was also examined, although this was much harder to do. The acidity of the solvent was observed to have a big effect on the degree of current doubling which can be related to hydroxyl surface layer effects. All these effects could easily be explained by the model. A number of synergistic effects which are harder to explain were observed as well, for example, the increase in total current with the use of two current doublers bringing the ratio close to two. It was also noted that water added to the acetonitrile solvent usually used decreased the current doubling of methanol but also increased the quenching ability of dissolved oxygen.

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Correlation effects on Raman scattering from lowenergy vibrational modes in fractal and disordered systems. I. TheoryThe frequencies and intensities of the Raman spectrum of thermally polymerizing styrene were measured in order to confirm (or correct) the mode assignments in the literature and to observe the effect of polymerization on the Raman active modes. The spectra were measured over a period of three weeks while an originally highly purified sample of monostryrene was kept at about 100 'C. The polymer vibrations are identified with their monomer "origins" which are in turn compared to known benzene (or benzene derivatives) and ethylene (or vinyl group) vibrations.

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