The role of electron impact cross sections and radiation transport in modelling VUV radiation in Hg-rare gas discharges

Modelling of Hg-rare gas discharges for the purpose of describing fluorescent lamps has a long and distinguished history, dating from the middle of last century. With the advent of LEDs and the consequent phasing out of florescent lamps for general lightning, development of these models ceased. However, the current interest in discharges producing VUV radiation for environmental purposes have led to an increased interest in these lamps since, in addition to the 254 nm radiation that was the principal source of light in fluorescent lamps, they also produce some radiation at 185 nm. The net production of 185 nmradiation in these lamps is determined by the excitation of Hg atoms into the 31P1 state and the subsequent transport of the resulting photons to the wall. We describe the application of recent calculations of electron impact cross sections for the main levels of importance for the modelling, together with a model for radiation transport of 185 nm radiation developed during the ALITE (Advanced Light Research) Program in the early part of the century, but never fully exploited. Results from the model for the important discharge parameters (gas fill, mercury pressure, discharge current) will be presented.