The vibrational excitation to v=1 level of the ground electronic state X ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{\mathrm{g}}^{+}{}_{}{}^{}$ of nitrogen was measured in a positive column during the 40-μs pulsed electric discharge, and in the afterglow. The discharge was operating at 6 Torr pressure and at current densities in the range 0.7–6.4 A/${\mathrm{cm}}^2$. Temporal evolution of vibrational excitation was measured using coherent anti-Stokes Raman scattering (CARS). Vibrational temperatures were found to range from 700 to 4000 K. The results are in fair agreement with model calculations based on energy transfer to vibrational excitation. Vibrational temperatures of the ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{\mathrm{g}}^{+}{}_{}{}^{}$ state, obtained from direct CARS measurements, were up to a factor of 3 below those deduced from the second positive system emission.

• Received 18 April 1994

DOI:https://doi.org/10.1103/PhysRevA.50.2341