LiF measurements of N2(A3Σu+, v=0) decay in a N2-O2 rf pulsed post discharge

N2/O2 plasmas are currently investigated under a variety of excitation conditions (microwave, dc, rf) and devices (afterglow, pulsed discharge, jets). The stream of species from such plasma are used for surface treatments of polymers, silicon, steel etc. and for material testing under conditions simulating re-entry problems of space shuttles. The kinetics in N2/O2 plasma discharges is rather complex since, together with N2. O2, N, O, NO, N2O, NO2 ground state species, numerous excited states are produced. Because of this complexity most of the elementary kinetics have been studied in afterglow conditions selecting as much as possible single reaction channels. Particular attention has been paid to the energy transfer processes between atomic and molecular nitrogen metastable and O2 and O. N2(A,v) + O2 (or O), giving as main products N2O or NO has been one of the most investigated reaction pattern. Then, the branching ratio of various exit channels has been determined. However, questions remains still open about the values of the branching ratio measured for N2O formation channel, as well as about the role of N2(X,v) in the competition with N2(A) for NO and NO2 formation. We are interested in N2/O2 kinetics in rf pulsed discharge. In this contribution we present the measure by LIF of the decay of N2(A,v=0) in a (0-20%)O2-N2 mixture. We also monitor the behaviour of NO-γ emission band which is expected to be correlated to some extent to the N2(A) state decay by the processes: N2(A,v) + O → NO(X) + N (1); N2(A,v) + NO(X) → NO(A2 summation +) +N2 (2)