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Photoionization produces supra-thermal electrons, electrons with much moreenergy than is found in a thermalized gas at electron temperaturescharacteristic of nebulae. The presence of these high energy electrons maysolve the long-standing t^2/ADF puzzle, the observations that abundancesobtained from recombination and collisionally excited lines do not agree, andthat different temperature indicators give different results, if they survivelong enough to affect diagnostic emission lines. The presence of thesenon-Maxwellian distribution electrons is usually designated by the term kappa.Here we use well-established methods to show that the distance over whichheating rates change are much longer than the distance supra thermal electronscan travel, and that the timescale to thermalize these electrons are muchshorter than the heating or cooling timescales. These estimates establish thatsupra thermal electrons will have disappeared into the Maxwellian velocitydistribution long before they affect the collisionally excited forbidden andrecombination lines that are used for deriving abundances relative to hydrogen.The electron velocity distribution in nebulae should be closely thermal.

The abundance discrepancy factor and t^2 in nebulae: are non-thermal electrons the culprits?