The optical properties of some alkali metal tungsten bronzes from 0.1 to 38 eV

The optical properties of the alkali metal tungsten bronzes are investigated. A review of existing data and the interpretation thereof is presented. Our absorptivity or reflectivity data for two cubic Na bronzes and for a tetragonal K bronze in the energy range 0.1 to 38 eV are displayed; the data are Kramers-Kronig analyzed and the optical constants are obtained. When feasible, comparisons are made with the existing data for the bronzes as well as for ReO₃, which is structurally similar. The interpretation of optical constants is based on an existing band structure for ReO₃ and modifications thereto are suggested.