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Experimental measurements of Hg excited state densities and the positive column electric field have been made in a highly-loaded low-pressure Hg–Ar discharge for current densities ranging from 0.05 to 0.6 A cm−2 and Hg vapour pressures from 1.2 to 13.2 mTorr. Resonance level (Hg 6s6p 3P1, 1P1) and metastable level (Hg 6s6p 3P0, 3P2) column densities across the positive column have been obtained using white light absorption spectroscopy. The experimental results are compared with numerical predictions from two existing and independent codes. Several physical mechanisms, which are not generally included in numerical models of the Hg–Ar positive column, are suggested as possible causes of the observed discrepancies.

Low-pressure gas discharge modelling is reviewed, both from a historical perspective and for current industrial applications. An ovetview of the basic mathematical and physical models used to describe low-pressure discharges is given, together with a summary of the most common numerical techniques which have been adopted. Modelling of the oc glow discharge and discharges maintained by high-frequency (RF and microwave) electromagnetic fields is reviewed, with illustrations of the validity of these models in predicting discharge properties and explaining and interpreting experimental results.

We have performed close-coupling calculations of electron scattering from the ground state of mercury atoms in the 4–500 eV energy range. Total scattering cross section and differential and integrated cross sections for elastic scattering and excitations of the 6s6p 1P1, 6s6p 3P0,1,2, 6s7p 1P1, 6s7s 1S0 and 6s7s 3S1 states are presented. Comparison with available experimental and theoretical results is presented. Good agreement with experimental differential cross sections in both shape and absolute values was found for most of the transitions.