A pulse radiolysis study on energy transfer mechanism in trioctylphosphineoxide-cyclohexane and tributylphosphate-cyclohexane systems by using benzophenone as a probe

Measuring the G values of ketyl radicals, benzophenone has been used as a probe to study the energy transfer mechanism in trioctylphosphineoxide(TOPO)-cyclohexane and tributylphosphate(TBP) CH systems under pulse radiolysis. Results showed that there was a process of energy transfer between the excited CH and TBP or TOPO, which coincided with our previous experiments on final product analysis. Rate constants (k) of energy transfer and G(CH*) (G value of singlet cyclohexane), which are k = 4.8 x 10(9) dm(3) mol(-1) . S-1, G(CH*) = 1.3 x 0.1 for TBP and k = 8.3 x 10(12) dm(3) mol(-1) s(-)1, G(CH*) = 1.4 +/- 0.1 for TOPO, were obtained by Stern-Volmer method. The abnormality of the rate constant for TOPO is discussed. Another process fitted with WAS equation was assumed to be geminate ions scavenging, and the alpha = 7.3, G(gi) = 3.8 +/- 0.1 for TBP, alpha = 649, G(gi) = 3.7 +/- 0.1 for TOPO, were gained. Meanwhile the mechanism of the latter process were also discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.Chemistry, PhysicalNuclear Science & TechnologyPhysics, Atomic, Molecular & ChemicalSCI(E)EI6REVIEW5455-4615