Abstract:

To determine the origin of the radiolytic product singlet state of hydrocarbons, the effect of water on the γ-radiolysis and pulse radiolysis of cyclohexane (C6H12)-tributylphosphate (TBP) solution was studied. In the γ-radiolysis of C6H12-TBP solutions, the addition of water can remarkably lower the yield of the acid product of TBP. The G value of the acid product dropped from 8.2 in the system containing no water to about 1.9 in the system saturated with water. This suggests that water inhibits not only the output of singlet TBP directly induced by the radiation energy absorbed by TBP itself, but also the energy transfer from the singlet C6H12 to TBP. In the pulse radiolysis of TBP-benzophenone (Bp) solution and C6H12-TBP-Bp solutions with Bp as a probe, the added water did not depress the yield of the radiolytic intermediate ketyl radicals. This phenomenon can be interpreted as that water reacted with the geminate ions [C6H12·+…e-] and [TBP·+…e-], giving ketyl radicals but depressing the formation of singlet C6H12 and singlet TBP. This might be direct evidence that most (G=1.3) of the singlet C6H12 and part (G=0.8) of the singlet TBP come from the recombination of geminate ions [C6H12·+…e-] and [TBP·+…e-], respectively. Due to its high polarity, water could be used as a specific scavenger of the geminate ions that can formexcited states via fast geminate recombination.

Key words: Cyclohexane, Singlet, Geminate ions, Radiolysis, Tributylphosphate, Water