Self-trapping of Radiation Produced Electrons

Abstract

THE problem treated here is the trapping of free electrons produced by ionizing radiation in dielectric systems. Detailed theoretical descriptions of the equilibrium properties of the solvated electron are available1–3, but its formation is still under discussion. Electrons are formed and thermalized in the coulomb field of the positive ions, but not fully recaptured by the ions. Magee4 considered the auto-ionization of the H3O radicals as a possible secondary source of electrons; Freeman5–7 assumed the electrons to be trapped in the defect sites of the medium at the instant of thermalization, while we thought8,9 that in polar dielectrics the escape of the electrons from the ions can be a free-energy decreasing, and therefore spontaneous, process. In our approach, the electrons which escape are treated as quasi-free, and the question of the kinetics and mechanism of electron trapping arises. Diffusion kinetic calculations on the radiolysis of water10,11 suggest very high initial hydrated electron densities, which require fast trapping processes.