Free ion yield observed in liquid isooctane irradiated by gamma rays. Comparison with the Onsager theory

We have analyzed data on the free ion yield observed in liquid isooctane irradiated by Co60 gamma rays within the framework of the Onsager theory about initial recombination. Several distribution functions describing the electron thermalization distance have been used and compared with the experimental results: a delta function, a Gaussian type function and an exponential function. A linear dependence between free ion yield and external electric field has been found at low electric field values (E<1.2 MV/m) in excellent agreement with the Onsager theory. At higher electric field values we obtain a solution in power series of the external field using the Onsager theory.