Refraction and Dispersion of Thallium Bromide Iodide

The refractive indexes of a mixed crystal containing 45.7 mole percent thallium bromide and 54.3 mole percent thallium iodide were measured at three temperatures near 19, 25, and 31°C for wavelengths from 0.5770 to 39.38 μ. The data were fitted to Sellmeier dispersion equations and thermal coefficients of index were computed. Dispersion coefficients were determined at 25°. The results were compared with data on a similar crystal.