Photolysis of Liquid Water at 1849 Å

The photolysis of pure water and of aqueous solutions of alcohols (methanol, ethanol, and isopropanol) at 1849 Å, when the light is absorbed by the water, proceeds according toComplex chemical formulaThe quantum yield for the formation of the geminate pair (H+OH) is φ=0.45 at room temperature. Scavengers compete with the recombination of the geminate pair according to diffusive inhomogeneous kinetics. A value of 3.9×10−6 sec½ is obtained for the Noyes parameter a, in agreement with theory. The results exclude direct interaction between scavenger and excited water molecules and also exclude molecular processes in the formation of H2. Solvated-electron formation has a quantum yield of ≤0.045. Isotope experiments support the conclusions. In the reaction with the alcohols, that of the OH radicals determines the competition with secondary geminate recombination. From the results a value of k(dim)/k(dis)=6.6 is obtained for the ratio of dimerization to disproportionation of CH2OH radicals.