Vacuum ultraviolet emission by active nitrogen. I. The formation and removal of N2(a1Πg)

The emission of the Lyman-Birge-Hopfield bands of N2(a1Πg) - X1∑g+), v' ≤ 6 in active nitrogen is shown to originate from the recombination of ground state nitrogen atoms. Two parallel processes occur: (а) A two-body inverse predissociation populates rotational levels J > 13 of N2(a1Πg), v' = 6, from which there is rapid rotational and vibrational relaxation; this gives an emission intensity proportional to [N]2. (b) The reaction N(4S) + N2(B3Πg) = N2(a1Πg) + N(4S) (5) populates mainly lower levels of the a a1Πg state giving emission proportional to [N]3 which is enhanced by argon carriers. Some measurements on N2(a'1∑u-), v' = 0 are also reported.