Dispersion of optical properties of trigonal crystals belonging to the A4CdX6 family

The refractive indices of Rb 4 CdCl 6 , (NH 4 ) 4 CdCl 6 and Rb 4 CdBr 6 crystals were determined in the visible range. The results were analyzed using a model of an effective one-electron oscillator. The possibility of using Rb 4 CdBr 6 , which exhibits an isotropic point as a material for a narrow-band optical filter, was studied