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Abstract:
Quantum-size semiconductor microcrystallites of ZnCdS and CdS in aqueous and isopropanol solution were optically excited using intense sub-picosecond UV laser pump pulses. Broad-band optical probing monitored the yield of electron emission and the build-up of primary photochemical products. With typical pmp fluences of femtosecond light pulses multiple photons are absorbed by one quantum-dot leading to a quantum yield of up to 0.3 of photogenerated electrons. The yield curves, as a function of pump fluence, are described by a simple kinetic model which involves the trapping-rate constant and a maximum number of electrons which can be emitted per particle. This model is shown to be consistent with thermodynamic considerations.
