We report integral cross sections (ICSs) for electron impact excitation of the A 3 + u , B 3 g , W 3 u , B 3 − u , a 1 − u , a 1 g , ω 1 u , C 3 u , E 3 + g and a 1 + g electronic states of N 2 . The present data, for each state, were derived at five incident electron energies in the range 15-50 eV, from the earlier crossedbeam differential cross section (DCS) measurements of our group. This was facilitated by using a molecular phase shift analysis technique to extrapolate the measured DCSs to 0 • and 180 • , before performing the integration. A comprehensive comparison of the present ICSs with the results of earlier experimental studies, both crossed beam and electron swarm, and theoretical calculations is provided. This comparison clearly indicates that some of the previous estimates for these excited electronic-state cross sections need to be reassessed. In addition, we have used the present ICSs in a Monte Carlo simulation for modelling the behaviour of an electron swarm in the bulk of a low current N 2 discharge. The macroscopic transport parameters determined from this simulation are compared against those measured from independent swarm-based experiments and the self-consistency of our ICSs evaluated.

A Monte Carlo simulation method has been developed and tested using the ramp model gas proposed by Reid (1979). This method is particularly useful for investigations in gases which must be modelled using many cross sections. This paper reports various phenomena associated with Townsend discharges in ExB fields in nitrogen. Of particular interest is the relative importance of terms in the density gradient expansion of the electron energy distribution function. Simulations are conducted to assist in the interpretation of data from experimental techniques, particularly the 'photon flux' method.

An approach for avoiding the problem of environmental uncertainty is tested using data from the TESPEX experiments. Acoustic data basing is an alternative to the difficult task of characterizing the environment by performing direct measurements and solving inverse problems. A source is towed throughout the region of interest to obtain a database of the acoustic field on an array of receivers. With this approach, there is no need to determine environmental parameters or solve the wave equation. Replica fields from an acoustic database are used to perform environmental source tracking [J. Acoust. Soc. Am. 94, 3335-3341 (1993)], which exploits environmental complexity and source motion.

Spatial variations of the relative excitation rates for two electronic states of molecular nitrogen have been measured for a point source Townsend discharge. The ratio of these rates shows a spatial dependence which is explained in terms of an electron con,centration gradient expansion of the energy distribution function. The electronic states were chosen to have quite different threshold energies such that the ratio would be sensitive to small changes in the electron energy distribution. A model for secondary electron production is used to explain the significant influence of secondary electrons in the outer regions of the discharge.

The photon flux technique has been used to study the cathode region of a steady-state Townsend discharge. Spatial variations in the radiation emitted from the C3fIu and B2.r~ states of molecular nitrogen were detected in the vicinity of the cathode for EIN"" 331 and 555 Td. In particular, the second positive emission at 337·1 nm is similar to the Holst-Oosterhuis layers observed in rare gas discharges. Monte Carlo simulations describe qualitatively the experimental results. However, modification of the assumed cross sections is required to improve quantitative agreement between simulation and experiment.