Optical Excitation of Phosphorus Vapour

Abstract

ON illuminating the vapour of phosphorus by the light of various sparks, we obtained a fluorescent emission in the region 3500–1900 A. The vapour was contained in an evacuated and sealed quartz tube into which a quantity of carefully dried white phosphorus distilled in vacuo was previously introduced. The temperature and pressure of the vapour could be varied independently by an oven and a water bath. In order to obtain the fluorescence, heating of the vapour up to 600°–700° C. was found to be necessary, the vapour pressure being kept low (c. 0.1 mm.). The phosphorus molecules, which consist normally of four atoms (P₄), dissociate under these conditions into diatomic molecules (P₂) to an appreciable amount.