Dember Effect in Silver Chloride

The Dember effect has been investigated in silver chloride using a chopped light-ac amplification system of measurement. The effect has been resolved into a self-sustaining component which reaches a steady state (for a particular wavelength and intensity of incident light) and a nonself-sustaining component which decays with time. The steady-state self-sustaining effect has been found to be of only one polarity (normal polarity) when the illuminated face of the sample is coated with silver, but of both polarities when the illuminated face is not coated. The normal or positive polarity self-sustaining effect shows up at a shorter wavelength and the inverse self-sustaining effect at longer wavelengths, both in the vicinity of the optical absorption edge. A possible explanation for this behavior based on the existence of surface states is suggested. In the coated sample, the normal polarity effect was found to exhibit a peak at a wavelength of about 0.383 μ at $T=88\mathrm{}°$K.