Investigation of Plasma Excitation. Volume II. Microwave Plasmas.

Abstract : Two different commercially available microwave applications were used to excite plasmas in electrodeless discharge tubes. Plasmas in a variety of gases and gas mixtures were investigated, including mercury, mercury bromide, xenon and hydrogen chloride, thallium iodide and mercury, thallium iodide and xenon, and sulfur. Approximately 35% of the total emission from tubes containing mercury and metallic halide additives occurred in the ultra-violet (220-350 nm). However, extensive self-trapping occurred, and the emission was greatest in tubes with low partial pressures, about 100 Torr of the component materials. Pulsed discharges in mercury bromide produced emission from mercurous bromide, but the application of continuous microwave power resulted in total dissociation and the observed emission was due to atomic mercury. Pulsed microwave discharges in tubes containing xenon and hydrogen chloride resulted in emission from two bands of the xenon chloride excimer. No excimer emission was seen from discharge tubes containing xenon and thallium iodide, or mercury and thallium iodide. In both cases, the density of the volatile component could not be increased with the available equipment to the value necessary for excimer formation. Discharges in tubes containing sulfur resulted in emission from diatomic sulfur which extended from 280 nm to 500 nm.