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Summary form only given. The chemical oxygen-iodine laser operates on the 1.315 mum I(1P12) rarr I(2P32) transition in atomic iodine; and is pumped by reactions between O2(1Delta) and molecular and atomic iodine. In electrically excited COIL lasers, (eCOIL), O2(1Delta) is produced in a plasma followed by injection of I2 in the afterglow containing the excited oxygen. The flowing afterglow additionally contains atomic O from dissociation of O2 in the plasma. The O atoms lead to dissociation of I2 and quenching of excited states, particularly the upper laser level, I*. While O atom helps in dissociating I2 thereby reducing the amount of O2(1Delta) required to achieve positive gain, it is also a quencher of I*, so managing the amount of O in the afterglow is necessary to maximize the laser gain. Additives such as NO and NO2 are effective in managing the O atom density and I inventory. These species consume O and I atoms by cyclic reactions involving O, NO, NO2, I2 and IO. In this paper, we report on results from a computational investigation of radiofrequency (rf) discharges and their flowing afterglows in He/O2 mixtures with NO and NO2 additives. The investigations were conducted with plug flow and 2-dimensional models. Scaling of O, O2(1Delta) and I* densities, and laser gain, while varying the mole fractions of NO injected through the discharge, and NO and NO2 injected downstream will be discussed reported. We found that moderate amounts of NO flowed through the discharge (< 10-20%) did not significantly change the discharge kinetics but did reduce the amount of O, and hence O3, downstream. The proper amount of NO and NO2 injection can maximize the gain even though O2(1Delta) densi- - ties may be lower for those cases due to consumption of ground state I and reducing the amount of O2(1Delta) required for I2 dissociation. The consequences of power and mole fractions on the production of I*, and system sensitivity to the rates of some important reactions, will also be discussed.