Measurement of the relative mobility of geminate ions in ethereal solutions of aromatic compounds using the fluorescence response of the solutions to pulsed irradiation.

This work examines the possibility of using the fluorescence response of irradiated solutions of luminophores and the effect of an external electric field on the fluorescence decay to determine the mobility of geminate radical ions when using aliphatic ethers as the solvents. As an example, p-terphenyl solutions were studied in a series of ethers (diethyl, dibutyl, methyl tert-butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, eucalyptol, and 1,2-dimethoxyethane). Verification of the nature of the charge carriers in the irradiated solutions was made by means of the method of the time-resolved magnetic field effect in recombination fluorescence of spin-correlated radical ion pairs. It was found that at a p-terphenyl concentration of about 10 mM, the observed fluorescent response from the solutions, in most cases, was due to the recombination of radical ions formed from the aromatic solute. The relative mobility of p-terphenyl radical ions in ethers was estimated by using a stochastic computer simulation of the radiation spur composed of 4 primary ion pairs. The ions' mobility was found to be dependent on solvent viscosity in accordance with Walden's rule, with no noticeable effect of solvent polarity.