Fluorescence of Fluorite and the Bivalent Europium Ion

Abstract

EXPERIMENTS conducted in this Institute¹ had led to the conclusion that the blue fluorescence of fluorite excited by filtered ultra-violet light is due to traces of europium under the influence of radioactive substances, and that a yellow-green fluorescence which some fluorites show at the temperature of liquid air—especially those from acid magmatic rocks—is, in the same way, due to ytterbium. As these rare earths are those most readily obtained in the bivalent form², as further the reducing action of Becquerel rays is well known, and as the blue fluorescence can also be obtained in CaF₂ containing europium, simply by reduction through heating, the hypothesis was put forward that these broad radio-photofluorescence bands are to be ascribed to the bivalent forms of the rare earths.