Investigation of the Infrared‐Active Lattice Vibration in SrCl 2

SrCl 2 , single crystals were grown by the Czochralsky method. Their reflectivity at 300 K and transmission at 4.2 K were measured for frequencies from 10 to 930 cm −1 and 10 to 150 cm −1 , respectively. The reststrahl band found in the reflection spectrum has been analyzed by means of a classical oscillator model. In addition, a Kramers‐Kronig analysis was performed since a satisfactory fit could not be achieved with the classical model. The frequencies of the TO‐mode and the LO‐mode were determined to be 138 and 233 cm −1 , respectively. A pronounced shoulder on the reststrahl band was observed as is also the case for CaF 2 , BaF 2 etc. Its origin is discussed in terms of multi‐phonon processes. The results of the transmission measurements show that SrCl 2 , is transparent in the far infrared up to 110 cm −1 where the lattice absorption starts at 4.2 K.