Possible manifestation of proton disorder in d-KIO3·HIO3 crystal in its IR spectra

For getting more information about the behavior of hydrogen atoms in partially occupied sites in d-KIO3·HIO3, we have measured temperature-dependent infrared spectra of this crystal at 14–300 K in the spectral range of OH stretching and bending vibrations. It was found that n(OH) band (centered at,2800 cm21) has complicated profile which, at temperatures below 220 K, includes weak low-frequency satellites at its low-frequency slope. At 14 K, we have main peak n(OH) at 2766, satellites at 2606, 2485, and 2387 cm21, and strong 2d(OH) overtone peak at 2274 cm21 enhanced due to Fermi resonance. At the same time, the low-frequency slope of d(OH) band (centered at 1189 cm21) shows equidistant satellites separated with period of approximately 25 cm21. The observed features suggest anharmonic coupling between OH high-frequency vibrations and various low-frequency motions of the crystal lattice. q 2004 Elsevier B.V. All rights reserved.