EPR and luminescence studies of self-trapped holes in silver chloride

We have used electron paramagnetic resonance (EPR) to study the migration of photoproduced self-trapped holes for temperatures below 30K, where the migration can no longer proceed by classical phonon-assisted hopping, and therefore a tunneling mechanism dominates. The data show that the self-trapped hole migration rate reaches a minimum at about 30K, and increases with decreasing temperature down to about 10K, when shallow trapping of the holes dominates the migration. The magnitude of the observed migration is too small to be explained by a coherent tunneling model, e.g. (Yam. 84). Migration rates calculated from the theory of Kondo (Kon. 84a, b) for incoherent tunneling are the correct order of magnitude, but do not show the observed increase in the hopping rate for decreasing temperatures.;We have also used a new photoluminescence technique to study self-trapped hole migration near liquid nitrogen temperature. The spectra show both the usual electron-hole recombination luminescence in pure silver chloride and a new luminescence in copper-doped AgCl which can be excited by sub-gap light, and which is due to hole trapping at Cu...