Visible and Infrared Absorption Spectra of Uranium Dioxide

The absorption spectra for single crystal and polyerystalline UO₂ have been measured between 0.6 and 15 μm at room temperature. The spectrum for UO₂ resembles that of a typical semiconductor, opaque in the visible but transparent over a large portion of the infrared. An absorption edge is located at approximately 0.6 μm (2.0 eV). A large optical window extends from 3 to 13 μm. The absorption coefficient for single crystal UO₂ has been determined between 1.5 and 15 μm. A maximum value of 57 cm^-1 was measured at 1.70 μm with minimum values of 6 cm^-1 at 2.75 and 8 μm. The absorption coefficient of polyerystalline UO₂ at wavelengths less than 8 μm is estimated to be ten times larger than for single crystal UO₂.