Photoluminescence dating

These pigments are used in such diverse ways as in outdoor advertising, blacklight displays, and laundering: in the latter case, a residue of the “ Although lightning, the aurora borealis, and the dim light of glowworms and of fungi have always been known to mankind, the first investigations (1603) of luminescence began with a synthetic material, when barium sulfate (in the form of barite, heavy spar) and coal; the powder obtained after cooling exhibited a bluish glow at night, and Cascariolo observed that this glow could be restored by exposure of the powder to sunlight.The name , or “sunstone,” was given to the material because alchemists at first hoped it would transform baser metals into gold, the symbol for gold being the Sun.

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The excitation involves only the outermost electrons orbiting around the nuclei of the atoms.Of course, the atoms of every material are vibrating at room temperature already, but this vibration is just sufficient to produce temperature radiation in the far infrared region of the spectrum.With increasing temperature this radiation shifts into the visible region.Cascariolo’s phosphor evidently was a barium sulfide; the first commercially available phosphor (1870) was “Balmain’s paint,” a calcium sulfide preparation.In 1866 the first stable zinc sulfide phosphor was described.

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