Raman Spectra of Irradiated Alkali Bromate Crystals

Abstract

Pure undamaged NaBrO₃ crystals shows four Raman lines arising from the internal oscillations in the BrO₃ ion besides a few other Raman lines due to lattice oscillations. On radiation damage by X-rays or γ-rays some new lines in the crystal are observed. Two of these at frequencies 680, 925 cm⁻¹ are of particular significance. It is postulated that by irradiation certain number of BrO₃ ions which initially have a pyramidal stucture loose the bromine leaving the three oxygen atoms at the corners of an equilateral triangle. Such a postulate leads to a satisfactory explanation of the appearance of the two new lines as it is well known that an equilateral triangular structure should exhibit two normal oscillations, both of which are Raman active. Correlated optical and IR studies lend support to such an interpretation.