Abstract: The secondary reaction kinetics processes of free radicals initiated by photoinduced electron transfer occured on the surface of semiconductor superfine particles were studied by means of ESR method. The results indicated that a lot of free radical reactions can be conveniently initiated with the help of COO^-· ion radical produced in the colloid system of Cadmium Sulfide(CdS) containing water soluble oxalate, and the rate constants of reactions of ion radical COO \+-. with other compounds may be calculated out according to the known rate constants of the addition reaction between spin trap DMPO and ion radical COO^-·, so as to develop a simple and effective approach for studying the kinetics of free radical reactions. Obviously, this method shall be extensively used in the research of other kinetics systems of free radical reactions taken place in condensed phase.

Key words: Cadmium Sulfide, Colloid, Oxalate, Photoreaction kinetics, ESR