Abstract

The purpose of the present investigation was to obtain data concerning the duration of phosphorescence of minerals. Some minerals with protracted emissions have been discovered and the features of their phosphorescence determined with dark-adapted eyes, and in some cases, with photographic film.

Studies have shown that the phosphorescence caused by a short exposure to 2437A ultraviolet rays will continue for a long period of time. Dark-adapted eyes were used to determine the duration of colored and colorless phosphorescence and photographic film was used to obtain phosphorographs and thereby record the emission of light long after it became imperceptible to the eye. Protracted phosphorescence has been discovered in calcite, fluorite, spodumene, wernerite, willemite, and synthetic phosphors. After an initial exposure of one minute, Texas calcite emitted an afterglow which was distinguishable to dark-adapted eyes for 4600 hours and was capable of producing a photographic image after more than 512 years. Fluorite from Trumbull, Connecticut, similarly exposed, continued to emit a phosphorescence perceptible to the eye for more than four years. The Texas calcite, fluorite, and spodumene are still phosphorescing.

Data on color and duration of visible phosphorescence of natural minerals are tabulated.

© 1950 Optical Society of America

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References

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  1. E. N. Harvey, Living Light (Princeton University Press, Princeton, 1940).
  2. J. DeMent, Fluorochemistry (Chemical Publishing Company, New York, 1945).
  3. E. L. Nickols and et al., (1938).

DeMent, J.

J. DeMent, Fluorochemistry (Chemical Publishing Company, New York, 1945).

Harvey, E. N.

E. N. Harvey, Living Light (Princeton University Press, Princeton, 1940).

Nickols, E. L.

E. L. Nickols and et al., (1938).

Other (3)

E. N. Harvey, Living Light (Princeton University Press, Princeton, 1940).

J. DeMent, Fluorochemistry (Chemical Publishing Company, New York, 1945).

E. L. Nickols and et al., (1938).

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Figures (3)

Fig. 1
Fig. 1

Phosphorographs. Phosphorescence of calcite, Chisos Mountains, Texas. Specimen exposed to ultraviolet rays for 1 minute. (a) Specimen on film during the 410 1 2 to 419 hour interval. Temperature range 68°–72°F. Total exposure 8 1 2 hours. (b) Specimen on film during the 24672 to 26712 hour interval. Temperature range 67°–78°F. Total exposure 2040 hours. (c) Specimen on film during the 49757 to 55016 hour interval. Temperature range 62°–78°F. Total exposure 5259 hours.

Fig. 2
Fig. 2

Photographs. Phosphorescence of calcite, Chisos Mountains, Texas. Specimen exposed to ultraviolet rays for 1 minute. (a) Photograph of specimen in daylight. (b) Photograph of specimen fluorescing in 2537A ultraviolet. (c) Photograph of specimen phosphorescing after excitation by 2537A ultraviolet.

Fig. 3
Fig. 3

Phosphorographs. Phosphorescence of calcite, Chisos Mountains, Texas. Specimen exposed to ultraviolet rays for 1 minute. (a) Specimen on film during the 7176 to 7696 hour interval. Temperature range 69°–78°F. Total exposure 520 hours. (b) Specimen on film during the 24190 to 26230 hour interval. Temperature range 66°–72°F. Total exposure 2040 hours. (c) Specimen on film during the 49275 to 54534 hour interval. Temperature range 62°–78°F. Total exposure 5259 hours.

Tables (3)

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Table I Duration of visible phosphorescence color.

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Table II Color and duration of visible phosphorescence of natural minerals.

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Table III Filters used for radiometry.a