Decay of the Concentration of Photoexcited Holes in Silver Bromide

The reaction between a deposit of silver and the bromine formed by holes migrating to the surface of a silver bromide crystal is used to verify the existence of mobile holes. The sensitivity of the method is greatly increased by a subsequent chemical treatment of the deposit. The method is used to study the concentration‐decay curve of holes which are generated by a light flash. For the different samples tested, the effective lifetime, as determined from the initial slope of the decay curve is found to be about 10−4 s. It is shown, however, that a small fraction of the holes remains mobile up to about 10−2 s after their generation. This suggests that the concentration‐decay is not likely to be described by a simple recombination mechanism.