Longitudinal Optical Phonons in CaF2, SrF2, and BaF2

1 November 1964

journal article
research article
Published by AIP Publishing in The Journal of Chemical Physics

Vol. 41 (9) , 2836-2837
https://doi.org/10.1063/1.1726360

Abstract

Off‐normal reflection spectra of thin films of CaF₂, SrF₂, and BaF₂ deposited on a silver substrate have been obtained. They exhibit decreased reflectivity at the long wave limit of the longitudinal optical branch. The values so obtained are in agreement with the predictions by the Lyddane—Sachs—Teller relation. They are also in agreement with vibrational levels obtained from vibronic data for SrF₂:Sm²⁺ and BaF₂:Sm²⁺. The observed longitudinal optical phonons are at 466 cm^—1 in CaF₂, 366 cm^—1 in SrF₂, and 319 cm^—1 in BaF₂. The close agreement between vibronic data and direct observation of these vibrations is considered further evidence that a good model for these vibronic transitions must consider vibrations of a relatively large segment of crystal and not merely nearest neighbors.

Keywords

This publication has 6 references indexed in Scilit:

Vibronic Spectra of Sr $F_{2}$ : ${Sm}^{2 +}$ and Ba $F_{2}$ : ${Sm}^{2 +}$
Physical Review B, 1964
Infrared Absorption at Longitudinal Optic Frequency in Cubic Crystal Films
Physical Review B, 1963
Infrared Properties of Ca $F_{2}$ , Sr $F_{2}$ , and Ba $F_{2}$
Physical Review B, 1962
Absorption and Fluorescence of ${Sm}^{2 +}$ in Ca $F_{2}$ , Sr $F_{2}$ , and Ba $F_{2}$
Physical Review B, 1962
Raman spectrum of fluorspar and its temperature variation
Proceedings of the Indian Academy of Sciences - Section A, 1950
On the Polar Vibrations of Alkali Halides
Physical Review B, 1941