Optical Absorption and Luminescent Emission of theI−Center in AgCl

The optical absorption and luminescent emission of AgCl crystals doped with small concentrations of AgI have been investigated. In such crystals, a narrow absorption band with intensity proportional to the iodide content can be resolved from the AgCl lattice absorption at low temperatures. Excitation in this (3.13-eV) band at low temperatures produces a distinct emission band peaking at 2.67 eV. The oscillator strength is found to be low (4×${10}^{-3\mathrm{}}$), whereas the radiative lifetime is rather long (6 μsec). A model is proposed in which the excited electronic states for absorption and emission are effective-mass states resulting in small overlap with the closed-shell ground state.