IR spectroscopy of KBr salt and crystals

Abstract

The IR absorption spectra of the KBr salt pellets of different purity and crystals grown of them were investigated in the region of 400…4000 cm⁻¹. It was found that by the IR spectra of the KBr salt pellets suitable for growing optically pure crystals one can evaluate the KBr salt quality. Revealed in the IR spectra are not only the impurity oxygen-containing molecular anions and the adsorption water but also, indirectly through them, the most dominating cations of sodium, barium and calcium. Determined was the concentration, beginning from which sodium ions are observed in the IR spectra of the KBr salt pellets. The coefficient of proportionality between the concentration of sulfates in the KBr salt and the absorption coefficient of SO₄²⁻ ions at the frequency of deformation vibration n₄ was found. The latter allows to estimate quantitatively the sulfates in the KBr salt.