Formation of color centers during growth of alkali-earth fluoride crystals

New bands within the ranges of 1900–2200 and 700–1000 cm^–1 have been discovered in the IR absorption spectra of crystalline alkali-earth fluorides. It is found that the defects responsible for the high frequency bands facilitate the formation of color centers during crystal growth. These bands are presumably caused by valence vibrations of CO molecules. The low frequency bands are attributed to molecular complexes which contain oxygen-vacancy dipoles.