A Tomographic Investigation of Variations in the Excited State Populations of E x B Discharges

A comparison of the spatial distribution of emissions from two molecular nitrogen electronic states of markedly different threshold energies has been made in a non self-sustained Townsend discharge in an ExB field. The spatial mapping has been performed using a combination of the 'photon flux' technique and reconstructive tomography. Observed differences in the spatial distribution of the two excited states are interpreted in terms of the gradient expansion of the energy distribution function. Comparisons made with the results of two-model simulations confirm this interpretation.