A far-infrared investigation of cathodochromic sodalite

Sodalite absorption bands in the 50–350 cm −1 region were studied using Fourier transform spectroscopy. Vibrational modes were identified using chemical substitution, H 2 and vacuum-annealing, and coloration studies. A bromosodalite band at 294 cm −1 was assigned to an Si—O—Al mode based on Ge substitutions for Si. A bromosodalite band at 200 cm −1 is assigned to an Na—cage vibration based on previous H 2annealing studies and chemical substitution of Ge for Si, Ga for Al and Cl and I for Br. A 107 cm −1 band is the Na—Br related vibration, and substitution of 100% Cl for Br moved this band to 111 cm −1, H 2 and vacuum-annealing studies show a correlation between the amount of Br removed from bromosodalite during annealing and the area of the 107 cm −1 band. A band at 68 cm −1 is the Na—Br mode based on 100% substitution of Cl for Br. Coloration studies in the 50–150 cm −1 region show no changes attributable to F-center formation.