Study of IR Spectroscopy of Crystalline Materials Structure Used in Laser Shutters

Abstract

The IR absorption spectra of hexagonal crystals of lithium iodate α-LiIO3, used in laser shutters for ship wiring, where the quality, transparency and power of laser radiation are of great importance, are studied. The transmission spectra allowed us to determine the width of the crystal band gap 4.37 eV along the Z-axis (C6 [0001]) and 4.46 eV along the axis perpendicular to the Z axis. The activation energies and the wavelength of the vibrational centers associated with the vibrations of the H3O+, OH-, H2O groups, heavy D2O and semi-heavy molecules HDO are determined. It is established that the band 1450-1650 cm-1 is a superposition of at least two broad absorption maxima centered at ~1550 and ~1600 cm-1. It was experimentally established that the ratio of the absorption coefficients of these bands was ~1:1 (75:74 cm-1) for crystals grown in H2O, and ~2:1 (161:84 cm-1) – for crystals grown in D2O. This allows us to assume that in a lithium iodate crystal grown in D2O, the bands 1550 cm-1 and 1600 cm-1 correspond to the vibrations of the bound HDO and H2O molecules, the band 1150 cm-1 corresponds to the vibrations of heavy water molecules. The results of the study allowed us to propose a mechanism of transport and translational diffusion of protons and to determine the presence of heavy water molecules in crystalline materials, as well as to diagnose the quality of laser crystals.