Dielectric permeability <$Eepsilon sub 0> of <$Ebeta>-alanine (<$Ebeta>-Ala) single crystals is studied with the IR spectroscopy technique and the appropriate calculations. We have calculated the dielectric permeability from the reflectance spectra, using the dispersive analysis and the harmonic multi-oscillator model. The calculations of <$Eepsilon sub 0> from the reflectance spectra of (010) <$Ebeta>-Ala crystal plane in the <$E400~-~4~000~ roman cm sup -1> region have earlier shown that it is impossible to achieve the <$Eepsilon sub 0> values experimentally measured in the microwave region (<$Eepsilon sub 0 sup { roman c } ~=~5,3,~ epsilon sub 0 sup { roman a } ~=~4,0>). The calculated data differ two times from those experimentally measured for one of the directions. The polarized IR reflectance spectra of <$Ebeta>-Ala single crystal and the transmittance spectra of the corresponding powder are detected in the <$E100~-~5~300~ roman cm sup -1> region. The account for the low-frequency modes (400, 321, 218, <$E180~ roman cm sup -1 }>) finally gives a possibility to obtain a good agreement between the calculated and experimental results. The large contribution to <$Eepsilon sub 0>, which is mainly due to the oscillator at <$E218~ roman cm sup -1>, is essential only for one of the alternative polarizations (E || the small axis of the (010) crystal plane). It seems to be associated with the H-bonded inter-molecular vibrations.

• Романюк Віктор Сергійович (фізико-математичні науки)

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