DETERMINATION OF N AND O ATOM DENSITY IN AR-N-2-H-2 AND AR-O-2-H-2 FLOWING MICROWAVE POST DISCHARGES

Number densities of N and O atoms have been determined using NO titrat ion in Ar-N-2, Ar-N-2-H-2, Ar-O-2 and Ar-O-2-H-2 flowing microwave (2 450 MHz) post-discharges at 300 and 1500 Pa. The NO titration scheme i s discussed from a kinetics point of view and applied to the high dilu tion of molecular gases in argon. The N/N-2 density ratio is enhanced by a factor 3 when small quantities of H-2 are introduced in Ar-N-2 di scharges. The high O/O-2 density ratio obtained in Ar-O-2 post-dischar ges (0.5 to 0.6) are probably due to adsorbed H2O that inhibits surfac e recombination of O-atom. The effect of H-2 addition in Ar-O-2 microw ave discharge at 1500 Pa is to decrease the O atom density by homogene ous reaction involving H atoms and OH radicals.