Ion-electron pairs in condensed polar media treated as H-like atoms

A model of radiation produced ion-electron pairs with an electron energy below about 1 eV is proposed for the description of electron moderation, self-trapping, and escape in condensed polar media. A discrete ion-electron pair is regarded as a ground-state H-like atom which interacts with the medium through polarization forces and by experiencing energy fluctuations. Slowly relaxing polarization makes electron energy decrease on the time scale of constant-charge dielectric relaxation. A strongly attracting polarization well is formed immediately upon ion pair formation owing to instantaneous polarization. Energy fluctuations can make the electron escape from the field of the ion, but not from that of the polarization well, i.e., the electron is already self-trapped when moderation and escape take place. The rate of electron moderation was found to agree with earlier estimates made by Fröhlich and Platzman. Solvated electron yields, by allowing also for initial recombination of energetically independent ion-electron pairs, were evaluated for a series of polar liquids and for ice as a function of ɛ_s²c_p^1/2, where ɛ_s is static relative permittivity and c_p is specific heat. By making use of one common adjustable parameter for all the systems discussed, good agreement was obtained with the majority of the experimental data.