The primary process ClO₃^-(+hv)->ClO^-+O₂ in the photolysis of aqueous ClO₃^- solutions

The quantum yield, PHI-1, in the primary process ClO3-(+h-nu) --> ClO- + O2 (1) and the sum of the quantum yields PHI-2 + PHI-3 in the primary processes ClO3- (+h-nu) --> ClO2 + O- (2) and ClO3- --> ClO2- + O(P3) (3) were measured in the steady-state photolysis of aqueous ClO3- solutions at 214 and 229 nm.

The ratio of the yields of ClO- and ClO3- in the reactions ClO2 --> ClO- + O2 and ClO2 + O- --> ClO3- (4) was determined by gamma-radiolysis of aqueous solutions of ClO2 at varying pH. The finding that the ratio between the yields of ClO- and ClO3- in reactions 4 equals the ratio between PHI-1 and the quantum yield, PHI-0 = 1 - PHI-1 - PHI-2 - PHI-3, for ClO3- returning to the ground state is taken as evidence that process 1 results from a cage-back reaction.

This result combined with recent studies of the radiolysis of KClO3 crystals suggest that the primary processes in the photolysis of aqueous ClO3- originate in a common process by which O- is expelled from ClO3- upon photoexcitation. The expelled O- may escape the solvent cage containing ClO2 (process 2), or react in a cage-back reaction (process 0 and 1).

During the expulsion of O- the photoproducts may convert to ClO2- and O(P3) (process 3).