A Spectrographic Study of Ultra-Violet Fluorescence Excited by X-rays

Abstract

Fluorescent spectra excited by x-rays.—(1) Ultra-violet. In order to photograph the spectrum, the specimen being studied was placed in front of the slit of a Fuess single-prism quartz spectrograph and was exposed to x-rays from a Coolidge tube with the target about 12 cm off. With the tube operating at.002 amp. and 50 kv and a slit width of.15 mm, exposures up to 15 hours were made. Over one hundred substances were tested. Fourteen double salts of uranium, 23 oxides, 50 other compounds and also anthracene, chrysoidine, eosin and fluorescine gave no ultra-violet fluorescence, though some show brilliant bands in the visible; but positive results were obtained with the chlorides of $\mathrm{Cd}$, $\mathrm{Cs}$, $\mathrm{Li}$, $K$, $\mathrm{Na}$, and $\mathrm{Rb}$, and also with $\mathrm{KBr}$, $\mathrm{KI}$, $\mathrm{Ba}{\mathrm{SO}}_4$, $\mathrm{Ra}{\mathrm{SO}}_4$ and $\mathrm{Ca}{\mathrm{WO}}_4$. NaCl gave a strong band with maximum at 2470A and CsCl gave a band extending from 5720 to 2340A with three maxima. Several willemite screens, some x-ray intensifying screens and one fluoroscopic screen also showed ultraviolet fluorescence. The intensity of fluorescent response decreased for successive exposures. (2) Visible fluorescence. One or more bands in the visible were emitted by all the salts showing ultra-violet fluorescence, except barium and radium sulfates, and also by ZnO, CdI, ${\mathrm{Cu}}_2$ ${\mathrm{I}}_2$ and HgCl and, of course, by the uranyl salts.