A simple three electron temperature model was applied to a one-dimensional, fully self-consistent model of a positive column discharge, as typically found in fluorescent lamps. It was shown that this model yields results that are in good agreement with reality, regarding important parameters such as the electrical conductivity, the electron temperature and the amount of radiation produced, and that it constitutes a significant improvement over a calculation based on a Maxwellian electron energy distribution function.

A novel method to describe diffusive processes in plasmas in local thermodynamic equilibrium (LTE) was developed, based on the transport of elements instead of individual species. This method combines the elegance of the LTE description of a chemical composition with the flexibility of explicit transport for each element. A simple model of a metal halide lamp containing Hg dosed with NaI is used to illustrate the method.

An existing LTE model (Johnston C W et al 2002 J. Phys. D: Appl. Phys. 35 342) of a high pressure sulfur discharge is improved upon by more accurate and complete treatment of each term in the energy balance. The simulation program PLASIMO (Janssen G M et al 1999 Plasma Sources Sci. Technol. 8 1, van Dijk J 2001 Modelling of plasma light sources: an object-oriented approach PhD Thesis Eindhoven University of Technology, The Netherlands, ISBN 90-386-1819-0), which is an integrated environment for construction and execution of plasma models, has been used to define and solve all aspects of the model. The electric field is treated as being dc, and the temperature dependent nature of species interactions is incorporated in determination of transport coefficients. In addition to the main radiative transition, , several others in S2 are included. These are , and . The S3 molecule is also included in the composition as an absorbing particle. Furthermore, radiation production is treated quantum mechanically. The principle improvement over the previous work is that both the position of the spectral maximum and the pressure shift are quantitatively described by the current model. Both are chiefly due to the presence of S3.