Compositional and structural control of tenebrescence

The effect of various compositional substitutions on the colour of long-lived F-centres in the sodalite structure has been investigated by the synthesis and characterisation of several phases of the general composition A8[M′M″O4]6[X,S]2. The visible-region absorption spectrum of the excited state, formed by 256 nm irradiation of the as-synthesised materials, shows a broad absorption whose position correlates with the dimensions of the sodalite cage occupied by the excited electron.