Modeling of Ba low pressure discharges

Summary form only given, as follows. The use of barium as a radiative emitter in low pressure discharge lamps has created considerable interest. Such lamps operate in a similar fashion to low pressure sodium or mercury lamps, in which the emitter is present as a low (a few to a few tens of micron) vapor pressure component in a rare buffer gas at several torr filling pressure. Mercury emits principally in UV, sodium in the visible, predominantly yellow, and neutral barium in the green, near the peak of the eye sensitivity curve. Discharges in Na and Ba can be highly ionized, leading to strong depletion of the emitting species at the discharge axis. This effect need not be as detrimental in Ba as with Na, since Ba has a number of strong ionic lines in the visible spectrum, which may assist in the production of white light. Detailed models of low pressure Na and Cs lamps have reproduced many of the experimental observations and a similar approach can be used to model Ba discharges. Further, the inelastic electron excitation processes in Ba are better documented than for most other elements. Results of a numerical model will be presented, using the best available atomic data, showing the predicted influence of discharge parameters on electrical characteristics, cataphoresis and radiation output in barium discharges.