Polarized IR reflectance spectra of the monoclinic single crystal K2Ni(SO4)(2)-6H(2)O: Dispersion analysis, dielectric and optical properties

摘要

Polarized IR reflectance spectra of K2Ni(SO4)(2)center dot 6H(2)O single crystal (belonging to the group of Tutton salts) were recorded at near-normal incidence. From the dispersion analysis performed on the spectra recorded from the ac crystal plane, mode parameters: transversal frequency, oscillator strength, attenuation constant and the orientation of the transition moment were determined. The polarized spectrum along the b crystallographic axis was also recorded and a dispersion analysis performed. Comparison between the spectroscopically obtained transition moment directions with those obtained from the structure data for various modes is discussed. All dielectric tensor component values were obtained for the whole mid-IR frequency range. Also, the real and the imaginary parts of the complex indexes of refraction for the waves with wave vector in the direction of the b crystallographic axis and in the ac plane (when the direction of the electric vector is oriented along the b axis) were found as functions of frequency. (c) 2007 Elsevier B.V. All rights reserved.