Optical detection of picosecond processes of formation of free carriers and primary photolysis products in AgBr(J) nanocrystals

Abstract

The fastest picosecond processes occurring in the electronic stage of photolysis in photosensitive AgBr(J) nanocrystals—the generation of free carriers and their initial capture by lattice defects and impurity centers with subsequent transition of captured carriers to deeper levels—were identified and quantitatively studied by methods of optical detection for the first time. The experimental characteristic times of these processes for AgBr(J) nanocrystals were shorter than 5 ps in the first stage and about 30 and 300 ps (for the generation and the capture of free carriers, respectively) in subsequent stages. The minimum durations of pulses of destructive nonactinic radiation at which dephotolysis processes can be reliably detected were estimated to be 20 ps for simultaneous illumination by pulses of destructive and exciting radiation and about 5 ps in the case of successive illumination. The decisive role of two-photon absorption in nonlinear processes of formation of hidden images under the action of picosecond pulses of nonactinic radiation was shown experimentally.