  The transient electric current of surfactants dissolved in a nonpolar solvent
is investigated both experimentally and theoretically in the parallel-plate
geometry. Due to a low concentration of free charges the cell can be completely
polarized by an external voltage of several volts. In this state, all the
charged micelles are compacted against the electrodes. After the voltage is set
to zero the reverse current features a sharp discharge spike and a broad peak.
This shape and its variation with the compacting voltage are reproduced in a
one-dimensional drift-diffusion model. The model reveals the broad peak is
formed by a competition between an increasing number of charges drifting back
to the middle of the cell and a decreasing electric field that drives the
motion. After complete polarization is achieved, the shape of the peak stops
evolving with further increase of the compacting voltage. The spike-peak
separation time grows logarithmically with the charge content in the bulk. The
time peak is a useful measure of the micelle mobility. Time integration of the
peak yields the total charge in the system. By measuring its variation with
temperature, the activation energy of bulk charge generation has been found to
be 0.126 eV.
