Optical absorbance and fluorescence in pure and doped ThO2

Fluorescence spectra resulting from uv excitation of pure, Ca 2+ ‐doped, and Y 3+ ‐doped ThO 2 were resolved into discrete bands at 395.4, 434.6, and 464.0 nm. These bands are related to absorption bands in the pure material at 238.9, 227.3, and 252.8 nm, respectively. The Ca 2+ ‐ and Y 3+ ‐doped ThO 2 specimens showed an apparent absorption edge at 240 nm (213 nm is the true edge in pure ThO 2 ). However, the fluorescence studies showed that this edge is, in fact, spurious, resulting from enhancement of the high‐energy absorbance bands by doping.