When activated with manganese alone, zinc fluoride emits an orange fluorescence under excitation by 2537A whose brightness is very weak because its peak excitation lies at 2200A. Other activators, cerium, tungsten, and titanium, shift the peak excitation to 2500–2600A and produce a higher absorption in the range 2000–2600A. The emission of tungsten and titanium lies mainly in the visible; that of cerium consists of a series of bands in the ultraviolet.
Combinations of these elements with manganese produce greater fluorescence brightness. With tungsten or titanium, the normal orange emission of manganese is increased manifold with no change in the spectral distribution nor in the unique exponential decay of its afterglow except that the decay is raised to a higher brightness level. With cerium, the individual emission of each activator persists, with no reduction in intensity of the ultraviolet cerium bands and with only a slight increase in the intensity of the manganese band.
As explanation of this apparent discrepancy, evidence was found that only tungsten and titanium are present in the same phase as manganese, namely, zinc fluoride. Cerium combines to form a separate phase, an aggregate of zinc and cerium fluorides.
© 1948 Optical Society of AmericaFull Article | PDF Article
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