Photons with energies of a few ev. can effect electronic transitions in molecules. These can store some of this excess energy in metastable states of varying life times and finally dissipate it. The dissipation may be a radioactive process (fluorescence or phosphorecence) or it may occur in a radiationless manner; such as, transfer to other molecules, heating effects or by photochemical reactions. Some of the phenomena following the absorption of electromagnetic radiation yield conveniently detectabe signals of information impressed by selective irradiation on the photo-sensitive memory material. Thus the photo-sensitive material can be utilized to receive writing information in the form of imaging electromagnetic radiation. This results in either
1. photophysical or
2. photochemical
changes which may be applied to the storage of information and its retrieval.

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Liquid development method of electrophotography was applied to the study on figures of discharge on the surface of dielectric plate in liquid insulators. The experiments were carried out with non-uniform electrode configurations, applying the standard impulse voltage, and voltage-current characteristics also were measured in various kinds of liquids.
According to the results in this work, it was found that, in order to obtain the discharge figure in liquid, it was necessary to use a dielectric plate which had high leakage resistance and higher dielectric constant than that of liquid insulator used, and that a phenol resin plate was the best material for the purpose of taking a discharge figure in insulating oil.
By employing this technique, it became possible to obtain a clear figure easily and to know the distribution and polarity of the residual charges, which were formed on the surface of the dielectric plate when an intensive discharge took place by high electric stress.

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Some theoretical analyses are given on the corona charging characteristics of an ideal sample having a homogeneous structure and a infinite leakage resistance, and various fundamental formulas obtained by the above analyses are listed in a table. Some discussions are also made about the effects of sample parameters such as donor density, dielectric constant and thickness on the Q-V curves of samples
Using a turn-table type equipment, measurements were made on the variations of surface potential V and electric charge Q during the process of corona charging of various kinds of ZnO binder layers and commercial electrophotographic paper. The values of layer parameters such as effective donor density, dielectric constant and avalanche starting field strength have been determined from the comparison between theoretical and experimetal Q-V curves.

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The adsorption process of fluorescein dyes, good sensitizers for electrophotographic zinc oxide layers, was studied by visible and infrared spectroscopic means. Thus crystalline, dissolved and adsorbed forms of the dyes were successively investigated by the above means in order to obtain informations on the structural changes of the dyes through the adsorption process from the solution to the surface of zinc oxide grains.
Exprimental results indicated that when the fluorescein dyes of free acid form, whether they were non-ionic lactoid or quinoid, were adsorbed on zinc oxide grains, structural changes of the dyes to the ionic quinoid form were accompanied, while disodium salt of them (ionic quinoid form) were invariant in the structure through the adsorption process. In other words, whether or not fluorescein dyes are ionic in the solution, they are ionized on the surface of zinc oxide, and the spectral sensitization occurs in almost the same manner.
Desorption experiments, in addition, suggested that the counter ion of the ionized dye on zinc oxide, as in the case of the former, was a zinc ion, while that was a sodium ion in the case of the latter.

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