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The fluorescence quenching under high excitation intensities has been studied in anthracene crystals. The singlet-singlet annihilation constant of (1 f 0.5) x cm8 s-l is calculated from the quenching of fluorescence induced by a nitrogen 16ns pulse laser (A = 3371 A). The main process of quenching under longer illumination (2 x lod s) is the interaction between singlet and triplet excitons with a rate constant of (7f4) x 10-8cmS s-l.HccneaosaHo Tyrueme $nyopecUeHUm KpHcTannoB aHTpaUeHa np11 BMCOKE~X YPOBHIIX BOa6yXneHHII. HOHCTaHTa CHHrJIeT-CEIHI' JIeTHOfi aHHHrEIn$lUHH, HafiAeHHaR I13 TYrUeHHR $JIYOpeCUeHlJHH, BO36yXaaeMOfi IlMnyJrbCaMIl a30THOr0 Jla3epaRBJIReTCH B3aHMOHefiCTBHe CElHrJleTHbIX H TpHllJIeTHbIX BKCHTOHOB C HOHCTaHTOP CKOPOCTH (7 f 4) x C M~ ceK-' .

The kinetics of photoelectrochemical hydrogen evolution at p-St single crystals m acidic aqueous soluliolls of electrolytes under pulse photoexciration was studied. Despite a low stability oF the silicon surface under the experimental conditions, a distract interrelation between the characteristic time of interlhcial charge transi~:r and stationary current was tbund. The determination of the characteristic transfer time does not need the detailed elaboration of generation-recombination processes in the semiconductor. The steady-state current density was shov, n to be determined both for the dark current and photocurrent by the. surface charge density.

From the measurements of quantum yield and fluorescence decay time of anthracene and naphthalene crystals for different pumping levels a t 300 K the rate constants of bimolecular

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