Intensity Dependent Effects in Silver Chloride: Bromine-Bound Exciton and Biexciton States

Varying the excitation power density over twelve orders of magnitude, the broad band recombination luminescence of AgCl containing 10 to 300 ppm of bromine impurities is investigated. Resonant excitation in the impurity‐induced and the free exciton absorption enables to discriminate recombination of the bromine‐associated self‐trapped exciton (STE(Br)) and intrinsic contributions. At very high powers a new band emerges which, on the basis of its nonlinear behaviour and lineshape, is ascribed to a bromine‐bound biexciton. The spectral features, including a zero‐phonon line of the STE(Br), allow a detailed analysis of all states in terms of binding energies and exciton radii. The results are compared with corresponding data in AgBr: I− and AgCl: I−.