A model is developed to determine the rate of electron transfer between high n molecular Rydberg states and ions of the same species under zero kinetic energy pulsed field ionization (ZEKE-PFI) experimental conditions. A simple hydrogenic model is used considering the two particles to be at rest with respect to each other. The results of accurate calculations for the u-g splitting in H-2(+) at low principal quantum numbers (separated atom) as a function of radius are extrapolated to large values of a relevant to typical ZEKE-PFI experimental conditions and used to determine the rate of electron transfer. Radius approximate to 5n(2) is arrived at as a simple expression to estimate the radius for a charge transfer rate of approximate to 10(8) s(-1) for lowest energy members of the Stark manifold (the fastest). Expressions are derived for other members of the manifold. Results are compared with the recent observation of 3% charge transfer in a ZEKE-PFI experiment by Alt et al.