Microwave photodielectric effect in AgCl

A microwave photodielectric effect was observed in pure AgCl powders on a fast time scale ($\sim 1\mu sec$) at both 90 and 295 K. It appears that this effect was caused by shallow trapping at a density of ∼${10}^{17}$ centers/${\mathrm{cm}}^3$, a number not inconsistent with other estimates of shallow trap densities in silver halides. This effect caused changes in the resonant frequency of a microwave cavity, which led to errors as large as 25% in the observed "fixed-frequency" microwave photoconductivity. A kinetic study of the photodielectric shift at 90 K indicates that the photodielectric effect is caused by shallowly trapped electrons in equilibrium with the conduction band for times $\gtrsim 10\mu sec$ after exposure. This suggests that the concept of "drift mobility" in AgCl is meaningful for these and longer times. For times $\lesssim 7\mu sec$ after exposure, a rapidly decaying photodielectric signal was observed, the origin of which is as yet unknown.