OPTICAL DIAGNOSTICS OF ACTIVE SPECIES IN N-2 MICROWAVE FLOWING POSTDISCHARGES

The nitrogen atom density is determined from NO titration and from the N-2 first-positive-band intensity. The main kinetic reactions which produce the N-2 first-positive-band emission in the afterglow are the following: [GRAPHICS] in an early afterglow at times 10(-3)-10(-2)s and N + N + N-2 --> N-2(B, upsilon') + N-2 in the full afterglow period (10(-3)-10(-1)s). From the N-2(B, upsilon'-A, upsilon '') first-positive-band intensity, parts of the above reactions have been established along a 2.45 GHz, 120 W N-2 flowing post-discharge at 5-130 hPa gas pressure and at 0.2-1 standard 1 min(-1) flow rate. It has been found that the NO titration method is only available in the late afterglow where the second reaction is dominant. By discriminating the second reaction from the first reaction, the first-positive-band intensity allows the N atom density determination in the post-discharge, along a larger domain than with NO titration including the end of the early afterglow. Furthermore, the first reactions contribute to produce highly excited levels up to N-2(B, upsilon' = 17, 18) whose vibrational distribution is given in the present paper. These levels, whose N-2(B, upsilon' > 13-15) states are autodissociative states are not created by the second reaction. Consequently, this is also a second method for specifying the afterglow parts where the above reactions are the dominant kinetic processes.