A dispersion relation is proposed and analyzed for the spectrum of cap
illary motion at a charged flat liquid surface with allowance made for
the finite rate of charge redistribution accompanying equalization of
the potential as a result of the wave deformation of the free surface
. It is shown that when the conductivity of the liquid is low, a highl
y charged surface becomes unstable as a result of an increase in the a
mplitude of the aperiodic charge-relaxation motion of the liquid and n
ot of the wave motion, as is observed for highly conducting media. The
finite rate of charge redistribution strongly influences the structur
e of the capillary motion spectrum of the liquid and the conditions fo
r the establishment of instability of its charged surface when the cha
racteristic charge relaxation time is comparable with the characterist
ic time for equalization of the wave deformations of the free surface
of the liquid. (C) 1997 The American Institute of Physics.