Enhancement of the Green Continuum of Hg by a Rare Gas

The green continuum of Hg vapor in a low current, positive column discharge has been found to be greatly enhanced by the presence of a considerable pressure of a rare gas (e.g., 50-mm argon). The effect is most striking for lower Hg pressures (e.g., at 50°C). At 215°C the light efficiency of the continuum reaches 41 lu/w. The continuum extends from 4000 to 6400A; its maximum occurs at 5130A at 115° and shifts toward the violet at higher temperatures. Very small amounts of gas impurity, e.g., 40 parts per million of ${\mathrm{N}}_2$ increase the brightness and also the voltage; larger amounts, e.g., 150 ppm ${\mathrm{N}}_2$, quench the brightness almost completely.