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Benzil has been irradiated in cyclohexane solution. The principal products are: benzoic acid; benzal-dehyde; phenyl cyclohexyl ketone; benzoin; benzoin benzoate; a compound tentatively identified as desyl benzoyloxydesyl ether; another compound not yet identified; and approximately one-third of the reacted benzil that was not accounted for. A small amount of unsaturation is also found. As long as there is enough benzil present (presumably to absorb all of the light) the benzil disappearance is linear with time. All products appear at the shortest times checked and so cannot be secondary products. If one neglects the benzoic acid approximately 19% of the benzoyl groups that react do so in the form of benzoyl radicals. No evidence for phenyl radical formation was found. The upper limit for the quantum yield of benzil disappearance at 366 mμ is 0.25. The benzoic acid does not arise directly during the photolysis but only when the solution is exposed to oxygen during the work-up. Preliminary experiments in cumene solution have shown that the amount of benzil lost for the same length of irradiation increases by a factor of about 1.5. In 2-propanol solution the increase is by a factor of 2.5. When 2-propanol is the solvent, a new product appears which is most probably the dimer of the ketyl radical which is formed when an excited benzil abstracts a hydrogen atom. This product is very unstable.

The new grating-type Au-n-type Si Schottky-barrier photodiode has been fabricated and analyzed. The device is constructed with a new structure of contact mask. The mask forms a grating of gold film over the contacting silicon substrate. The grating spacing is so chosen that even at zero bias the interfacial layer between the silicon substrate and the gold gratings is completely depleted. The device is fabricated on an n-type silicon wafer of ∼1300-Ω.cm resistivity, and the grating spacing is 12.5 µm. An analysis is performed to determine the I-V characteristics, the spectral dependence of the quantum yield, the responsivity, and the noise characteristics of the photodiode. It is found that without optimization the device has a bandwidth of ∼1 GHz and responsivity of 0.63 A/W at λ =0.9 µm.