  Electric field is a thermodynamic force that can drive collisional
inter-ion-species transport in a multicomponent plasma. In an inertial
confinement fusion (ICF) capsule, such transport causes fuel ion separation
even with a target initially prepared to have equal number densities for the
two fuel ion species. Unlike the baro-diffusion driven by ion pressure gradient
and the thermo-diffusion driven by ion and electron temperature gradients,
electro-diffusion has a critical dependence on the charge-to-mass ratio of the
ion species. Specifically, it is shown here that electro-diffusion vanishes if
the ion species have the same charge-to-mass ratio. An explicit expression for
the electro-diffusion ratio is obtained and used to investigate the relative
importance of electro- and baro-diffusion mechanisms. In particular, it is
found that electro-diffusion reinforces baro-diffusion in the deuterium and
tritium mix, but tends to cancel it in the deuterium and helium-3 mix.
