LiF単結晶の新製作法とその光学的性質

抄録

According to the procedures adopted for preparing the materials and making the crystals grow, single crystals of LiF are apt to include impurities, which bring about remarkable absorptions in near infrared and ultraviolet regions (at 2.8p, 200 mp or shorter wavelength and over the range from 250 mp to 300 my). Paying attention to the purifying method of materials, pure crystals are successfully made by a new type vacuum furnace, and the influence of atmospheric gas on the crystal growth is examined.
The crystallization of LiF is carried out by a modified Kyropoulos' method in dry nitrogen gas kept fresh by continued streaming, crystal growth being observed through a glass window of the vacuum furnace. The crystallization by this furnace is so feasible compared with Bridgman-Stockbarger's method that various other materials can be crystallized as well as LiF under respective growth conditions. As for the purification of LiF materials, three preparation methods were adopted and the one that started from lithium chloride and ammonium bifluoride was found most favorable. In crystals made from the purest materials, absorption below 200 my is very much weakened. In vacuum-grown crystals, in general, 2.8 p absorption in the near infrared and the absorption from 250 mp to 300mp are completely eliminated. Brief account of the properties of these absorption bands is given.