The transmission of lithium fluoride in the visible and ultraviolet may be considerably reduced by exposure to very intense ultraviolet radiation, electron bombardment or contact with a low pressure electrical discharge. Strong absorption bands with maxima at 5200, 3100, and 2500A and a gradually increasing absorption below 1800A appear after a few minutes exposure to electron bombardment or contact with the low pressure discharge. Since 75 hours exposure to the light of a hydrogen discharge tube caused only about a maximum decrease in transmission, lithium fluoride may be considered as satisfactory as fluorite for of 5 percent use in ultraviolet optical instruments. Since all of the absorption bands build up at about rate, the visible discoloration, faint yellow to deep red, may be used as an indication of the same the change in the ultraviolet. Lithium fluoride colored by irradiation may be useful as a filter in ultraviolet studies.
© 1937 Optical Society of AmericaFull Article | PDF Article
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