Formation and Decay of the Transient Species in Radiation Chemistry. Radiolysis of Alkyl Halide Systems

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Abstract
Biphenyl and trans-stilbene were irradiated by a pulse of 300 mA×0.5 μsec in two types of solvents, alkyl halides and methyltetrahydrofuran. The spectra obtained by n-butylchloride, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2-trichloroethane, and 1,1,2,2-tetrachloroethane were concluded to be those of the cations, while the spectra obtained by CCl4, 1,1,1-trichloroethane, and pentachloroethane were concluded to be due to something other than the cations. The spectra of o-terphenyl in 1,1,2-trichloroethane and in 2-methyltetrahydrofuran were different, the reason for this was discussed. The decay curves of the optical densities due to both the cations and the anions all exhibited first-order rates. The decay of the cation of the aromatic solute was concluded to consist of two processes, the transportation of the charged species and the neutralization of the ion pair thus formed. The rate-determining step is the neutralization process, the activation energies of which are 2.17 and 3.62 kcal/mol for trans-stilbene and biphenyl respectively. The transportation of the charged species was concluded to be not by the movements of the anion and the cation across the solution, but by the electron-trap- and hole-conductions, such as have been observed in semiconductors.