TWO-PHONON ABSORPTION SPECTRA OF SINGLE CRYSTALS OF THE CALCITE STRUCTURE AT LOW TEMPERATURES.
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Date
1969
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Volume Title
Publisher
Ohio State University
Abstract
The infrared spectra of single crystals of $NaNO_{3}, CaCO_{3}, CaMg(CO_{3})_{2}$ have been investigated at about $10^{\circ}K$ with polarized light in the spectral region between $700 cm^{-1}$ and $2300 cm^{-1}$. Besides the strong absorption bands corresponding to the inner vibrations of the $NO_{3}^{-}$ or $CO_{3}^{-}$ molecules, a great number of weaker bands were observed which are attributed to combinations of these inner vibrations with external lattice modes. The observed structure of these bands is attributed to transitions with wavevectors ending at the center and at the boundary of the Brillouin-zone. The observed transitions are compared with selection rules derived for certain points in the Brillouinzone and conclusions about the dispersion of the vibrational branches in these crystals are discussed.
Description
Author Institution: Department of Chemistry, Carleton University