  Alkali vapor cells with antirelaxation coating (especially paraffin-coated
cells) have been a central tool in optical pumping and atomic spectroscopy
experiments for 50 years. We have discovered a dramatic change of the alkali
vapor density in a paraffin-coated cell upon application of an electric field
to the cell. A systematic experimental characterization of the phenomenon is
carried out for electric fields ranging in strength from 0-8 kV/cm for
paraffin-coated cells containing rubidium and cells containing cesium. The
typical response of the vapor density to a rapid (duration < 100 ms) change in
electric field of sufficient magnitude includes (a) a rapid (duration of < 100
ms) and significant increase in alkali vapor density followed by (b) a less
rapid (duration of ~ 1 s) and significant decrease in vapor density (below the
equilibrium vapor density), and then (c) a slow (duration of ~ 100 s) recovery
of the vapor density to its equilibrium value. Measurements conducted after the
alkali vapor density has returned to its equilibrium value indicate minimal
change (at the level of < 10%) in the relaxation rate of atomic polarization.
Experiments suggest that the phenomenon is related to an electric-field-induced
modification of the paraffin coating.
