Optically detected electron spin resonance studies of electrons and holes involved in geminate recombination in non-polar solutions

Abstract

Optically detected electron spin resonance spectra have been used to identify geminate electrons and free holes in non-polar hydrocarbons. The temperature dependence of the spectra has been investigated in terms of excess electrons and also electrons solvated in clusters by water molecules. The line intensity of an excess electron increases with falling temperature, while the linewidth decreases with rising temperature. The signal from a hydrated electron is observed at higher temperatures in comparison with that from an uncaptured electron. Its intensity increases with the concentration of water in the solvent. The collapsed spectrum width has been employed to estimate the charge-transfer rate constants in the recombination of free holes in p-xylene and in benzene. The signals from holes are effectively suppressed by adding compounds with low ionization potentials. The suppression efficiency increases with the difference in ionization potentials between the solvent and admixture.