Abstracts of Technical Articles from Bell System Sources (01 October 1934)

Radio Engineering, June, 1934. Proc. I. R. E., August, 1934. Jour. Op. Soc. Am., August, 1934. 701 702 BELL SYSTEM TECHNICAL JOURNAL radiation, or whether the spectral selectivity is in the nature of a locally intrinsic emissive power, such as would be caused by an optical absorption band or an electronic transmission band. In order to answer this question, it is necessary to have emitting surfaces of a specular character. Such surfaces have not been prepared with the alkali hydrides, but it has been found possible to make the caesium-silver-oxide cells on specular plates of silver so that they retain their specular character in the final sensitized surface. 

Cells of this sort were used in this study, and have made possible a clear separation of the emissive singularities due to optical conditions and the singularities which may be described as intrinsic to the material. Both from their method of preparation and from their optical behavior, we have felt justified in considering the caesium-silver-oxide photoelectric cells prepared with specular silver surfaces as consisting of silver surfaces overlaid with a thick layer of transparent refracting material, on the top of which is a thin photosensitive layer. 

The silver plates, after oxidation, exhibit interference colors, the exact color depending upon the amount of oxidation. Viewed at an angle through a nicol prism, these oxidized plates exhibit the well-known properties of thin refractive layers on a metal base. Thus when the plane of polarization is changed from the plane of incidence to the plane perpendicular thereto, no change of hue takes place for small angles of incidence; but at large angles, the color changes to a complementary hue.