Photoelectric Emission from the Valence Band in AgBr

New data on the spectral dependence of the photoelectric yield from AgBr corroborate the threshold energy near 6 ev found in early work by Fleischmann. At higher energies, the yield rises in a reasonable way to plateau values above ${10}^{-2\mathrm{}}$ electron/incident photon. The emission is accordingly interpreted as originating in the valence band. Since the electron affinity of the crystal is then 3.5 ev and the band gap a comparable 2.5 ev, AgBr is an interesting type of photoemitter in which scattering of excited electrons by valence-band electrons (as in avalanche processes) is incipient near the threshold energy. AgBr is compared to extreme examples of strong and weak valence-band scattering.