M. Thomas
1997
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Abstract
Publisher Summary Strontium fluoride (SrF2) offers a wide range of transparency, from the ultraviolet to the long-wave infrared, with low reflectance loss and low dispersion. This combination of broad transparency and low dispersion is rare in optical-window materials used in infrared systems. SrF2 allows experimenters to conveniently perform initial system alignment in the visible and then switch to the infrared with only minor correction of the optical components. SrF2 also has good surface hardness and is not hygroscopic. It has a flexure strength between those of CaF2 and BaF2. It is a cubic crystal with the fluorite structure, space group Fm3m, with four formula units per unit cell. The atomic arrangement is strontium atoms occupy the 4(a) sites and the fluorine atoms occupy the 8(c) sites. Laser-calorimetry data indicates low-level absorption in roughly the middle of the transparency range of SrF2. The multiphonon absorption (multiple-quanta lattice vibrations) edge generally marks the end of infrared transparency.