Phosphorescence of Mercury Vapour

Abstract

LAST July I published in the Proceedings of the Royal Society an account of a persistent fluorescence of mercury vapour produced by excitation of “2536” light, obtained from a quartz-mercury arc lamp. I have recently placed the fluorescent vapour in a strong magnetic field, and find that when the mercury lamp is cooled and consequently the “2536” line is sharp, the magnetic field increases the intensity of the fluorescence several times. If the lamp is allowed to warm up so that the “2536” line becomes broadened and reversed, the opposite effect is obtained, i.e. the phosphorescence decreases in intensity with the field. In this latter case the field strength that produces the greatest diminution in intensity increases with the temperature of the quartz-mercury lamp. The ordinary fluorescence produced by the light from the cadmium spark is not affected by the magnetic field. I am at present working with the idea of obtaining a satisfactory explanation of the persistent fluorescence and the various phenomena connected with it.