Time scale considerations on the relaxation of electronic and vibrational energy distributions in a nitrogen afterglow

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Abstract
The relaxation of the electron energy distribution function (edf) in vibrationally excited N2 post discharges has been analysed by discussing the characteristic times necessary for « edf » to achieve and maintain a quasistationary state and by comparing these times with other important times corresponding to electron losses by dissociative recombination and diffusion to the tube wall. The calculated results show that the vibrational collisions can create a quasistationary « edf » in times of 10-7-10-6 s ( p = 5 torr, T = 500 K). This quasistationary state is characterized by a strong correlation between vibrational distribution and mean electron energy. It can last up to several 10-3 s till the electron density becomes too small as a result of recombination and diffusion. Comments of some earlier experimental results are finally given