Study of iodine atom production in Ar/CH3I dc glow discharges

A transverse flow dc glow discharge in Ar/CH3I mixtures was modeled using a plug-flow approximation and plasma evolution was computed within a frame of reference moving with the gas. Reduced electric field as a function of transportation length was determined using the condition of a constant power density in the discharge. Cathode fall (CF) was found by comparing modeled and experimental discharge voltages. It was shown that conditions in the plasma column are nearly optimal for iodine atoms production with the lowest required energy and larger energies observed in the experiment are due to energy loss in the CF. In the experiment, concentrations of iodine molecules were measured downstream of the discharge using laser-induced fluorescence. Iodine flow at the exit of the discharge generator consisted of 80-90% of iodine atoms and only of 10-20% of iodine molecules. A good agreement between modeled and measured concentrations was found.