VIBRATIONAL-RELAXATION OF N2(C,UPSILON)-STATE IN N2 PULSED RF DISCHARGE - ELECTRON-IMPACT AND POOLING REACTIONS

The decay of DELTAv = - 2 band sequence of N2 Second Positive emission system has been investigated in a N2 rf pulsed 500 Hz post discharge in the pressure range 0.1-3 Torr. The intensity of each band head of the sequence has been used to infer the N2(C, epsilon' = 0-4) relative vibrational distribution. The shape of the distribution varies significantly with the post discharge time and the pressure. A population inversion in the levels 0-1 and 2-3 characterizes the distributions measured at post discharge times higher than 100 mus. The distributions at the various post discharge times have been fitted by a model which takes into account three processes for the (C, upsilon') excitation: the electron impact from (X, upsilon) states by fast electrons (a), from (A, w) state by slow electrons (b), and the pooling reaction N2 (A, w) + N2(A,w') (c). In the discharge the excitation is predominantly given by process (a). At 1 ms in the post discharge the electronic process (b) still survives, and, together with process (c), provides excitation to C state.