Radiative Decay-Time of Bound Excitons in Silver Bromide

Abstract

Luminescence due to decay of iodine-bound exciton in AgBr:I⁻ is observed under irradiation of a Q-switched ruby laser and can be concluded as originated from interband two-photon transition process. Radiative decay-tome of the luminescence is studied as a function of temperature (2∼120°K), emission wavelength (460∼550 nm) and iodine concentration (2.1×10¹⁸∼5.3×10¹⁹ cm⁻³). The decay kinetics and its temperature dependence are found to be different between the two emission components in the emission spectrum; high energy component (∼495 nm) and low energy one (∼520 nm). The decay time at 2°K are (25±4)×10⁻⁶ and (16±3)×10⁻⁶s for high and low energy components, respectively, at iodine concentration of 2.1×10¹⁸ cm⁻³. The concentration dependence of relative intensity of the two components can be understood by assuming that the high energy component corresponds to exciton bound to isolated iodide ion and the low energy component to that bound to iodine pair.