CHARGES ON METAL-IONS IN GLASS

Since metal ions bear a charge equal to their spectroscopic oxidation state only in the gas phase, it is necessary to consider how the posit ive charge is reduced for the chemically combined ion and also to devi se criteria for assigning this charge. Here it is shown how interelect ronic repulsion energies, obtained from optical spectroscopy, can be e xploited, and the method is exemplified for the Tl+ ion to show how it s effective charge decreases with increasing basicity of the glass. Tr ends are reported for the alkali metal ions, especially in berate glas ses where two types of site have been shown to exist. Consideration is also given to the degree of negative charge, provided by the oxygen a toms of the glass, at sites for the metal ions.