By crystallizing with excess magnesium oxide the photo-luminescent efficiency of manganese-activated magnesium orthogermanate has been increased 500 percent. The emission spectra of these materials extend from 6100A to 6700A, and exhibit a unique fine structure consisting of four bands about 50A wide and having peaks approximately 90A apart. Small changes in composition leave the positions of the emission peaks invariant but greatly change the relative intensities of the peaks. This fine structure offers a valuable key to determining the optical transitions involved in the luminescence of manganese-activated phosphors. Manganese-activated zinc-magnesium fluoride phosphors exhibit under cathode-ray excitation the longest trulyexponential afterglow of any efficient known luminescent material. Crystallization of these phosphors under 100 atmospheres of hydrogen fluoride does not greatly alter their luminescent characteristics. Fluoride phosphors, particularly manganese-activated zinc fluoride, possess the unique feature among luminescent materials of being capable of evaporation and condensation in a vacuum to form thin uniform transparent layers without unduly affecting the luminescent efficiency.
© 1947 Optical Society of AmericaFull Article | PDF Article
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