Reciprocity Failure Effects in the Solarization Region

Abstract

Experimental data are presented showing that much heavier exposures are required to reach the region of solarization at high intensities than at low intensities. It is suggested that this is due to the combined effects of wastage at high intensities by direct recombination of electrons and holes and to the high efficiency of formation of surface silver relative to internal silver. Evidence is presented supporting both these suggestions. Further study has shown that the preferential formation of surface silver at high intensities can be attributed to the large number of shallow trapping sites brought into play at the grain surface. A low rate of supply of silver ions to internally trapped electrons may also be responsible in part.

In view of the difficulty in nucleation and growth of internal silver at high intnsities, owing to surface competition, and the difficulty in nucleation at very low intensities as indicated by ordinary reciprocity-failure data, a minimum of exposure to obtain a given degree of solarization is expected at an intermediate intensity. All materials examined showed this effect.