Electron temperatures in a pulsed electric discharge and the associated N2 electron excitation rate coefficients

Investigations of excitation processes of molecular nitrogen in pulsed electric discharges have been focused on the N2 first positive system (1PG) which corresponds to the transition, N2(B 3Πg→A 3Σ+u). Our observations indicate that collisions during the afterglow which follows the 4 μs current pulse couple the vibrational levels of the B 3Πg state with those of the overlapping triplet states (A 3Σ+u,W 3Δu, B′ 3Σ−u) by the intersystem collisional transfer of excitation (ICT). In order to model the effect of this process we must first estimate the relative direct electron excitation rates of these overlapping states. This, in turn, requires knowledge of the electron energies during the course of the electric discharge. We have used the Balmer series Hα/Hβ intensity ratio to measure the varying electron temperatures that occur during the pulse for a number of experimental conditions. The electron temperatures which we observe range from 5 000 to 11 000 K. This is below the temperatures for which electron excitation rate coefficients for N2 excited states have been tabulated previously, so we also present these coefficients for electron temperatures from 1 000 to 15 000 K.