# MEASURING UNIAXIAL SPECTRAL DIELECTRIC RESPONSE: APPLICATIONS TO CALCITE $CaCO_{3}$ AND TYSONITE $LaF_{3}$.

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 Title: MEASURING UNIAXIAL SPECTRAL DIELECTRIC RESPONSE: APPLICATIONS TO CALCITE $CaCO_{3}$ AND TYSONITE $LaF_{3}$. Creators: Parrish, J. F.; Perry, C. H. Issue Date: 1969 Publisher: Ohio State University Abstract: Often it is not possible or convenient to orient a crystal's optic axis precisely parallel or perpendicular to a large single crystal face. Furthermore, it can be shown both theoretically and experimentally that even rather small misalignments of an optic axis (less than five are degrees) can lead to large, easily measurable but possibly spurious effects. Nevertheless, quantitative and qualitative analysis of the measured spectra is possible, as it can be proved that the zeros (longitudinal optical frequencies) of the effective spectral dielectric response must occur at the zeros of the characteristic spectral dielectric response functions defined parallel and perpendicular to the optic axis, independent of the angle between the optic axis and crystal face. Moreover, the characteristic dielectric response functions can be calculated analytically from the experimentally measured effective spectral dielectric response functions of the ordinary and extraordinary rays reflected or transmitted by a single crystal face. The polarized far infrared transmittance and reflectance of calcite, which has strong anisotropics at high lattice frequencies ($\sim 1500 cm^{-1}$), and of tysonite, which has strong anisotropics at low lattice frequencies ($\sim 100cm^{-1}$), illustrate some of the effects predicted theoretically. Description: This work was supported in part by the U. S. Air Force (ESD Contract AF 19(628)-69-C-0081) and NASA grant NGR 22-011-051 at Northeastern University and the Joint Services Electronics Program (Contract DA28-043-AMC 02536 (E) at M.I.T. J. F. Parrish is a Visiting Research Associate, Department of Physics, Northeastern University. Author Institution: Research Laboratory of Electronics, Massachusetts Institute of Technology; Department of Physics, Northeastern University URI: http://hdl.handle.net/1811/15860 Other Identifiers: 1969-T-4