Molecular motion in the supercooled liquid state: ion pairs in slow motion

The dielectric relaxation behaviour of dilute solutions of tri-n-butylammonium picrate and tri-n-butylammonium iodide in o-terphenyl have been studied over a frequency range (1 to 105 Hz) in the supercooled liquid state. The ion-pairs are found to relax in this frequency range by a cooperative mechanism involving the solvent molecules, and the mechanism for this process is discussed. In addition, the thermally stimulated depolarization currents of electrets formed from the ion-pair solutions of the picrate have been studied and are shown to yield information on the motion of the ion pairs in the region of 10–2 Hz.