Excitation of vibrational and electronic states in a glow discharge column in flowing N2

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Abstract
The excitation and ionisation number densities of different states of N2 have been measured in a long positive column of a glow discharge in flowing N2 when the residence time of excited species in the column was varied between 5*10-4 and 2.5*10-1 s. The vibrational population of the ground state N2 (X 1 Sigma g+, nu ) and the electron energy distribution function (EDF) have been calculated for different values of gas pressure, electric field and electron densities. For residence times greater than 10-2 s the N2(X, nu ) and the EDF tails are strongly overpopulated. The vibrational population of the excited states N2(C3 Pi u, nu ') and N2+(B2 Sigma u+, nu ') have been experimentally determined by measuring the second positive and first negative band intensities. The measured N2(C, nu ') distributions are in good agreement with the calculated populations assuming that the C3 Pi u state is created by electron collisions and destroyed by radiative emission. The ionic lines emitted from N2+(B, nu ') have large intensities for long residence times t>10-2 s suggesting that the heavy particle reaction: N2(X, nu >or=12)+N2+(X) to N2(X)+N2+(B) is the main process.