Recombination Coefficients for Positive and Negative Ions

The dielectric constant of an ionized medium is decreased not merely by the presence of electrons but also by that of other free carriers, the positive and negative ions. In a highly electronegative gas discharge, the effect of the ions cannot be neglected and sometimes their contributions may swamp that of the electrons. Under such conditions, measurements of the recombination coefficient between positive and negative ions have been made in the afterglow following pulsed radio-frequency discharges in iodine and bromine vapours.. The recombination coefficient α i was found to be 1.47 × 10 -8 cm 3 sec -1 for iodine molecular ions and 1.85 × 10 -8 cm 3 sec -1 for bromine at room temperature. α 1 was constant over an extended pressure range and was found to be temperature dependent.