Effects of X-irradiation on the Principal Uranium Centre in Alkali Fluorides

Abstract

When fluorescing crystals of LiF and NaF containing hexavalent uranium and oxygen are X-irradiated the fluorescence is quenched and new absorption centres are created. There are strong absorption lines created at 562�8 nm in LiF: U, 0 and at 580�6 nm in N aF: U, O. These and other absorption lines have been studied by magnetic circular dichroism (MCD). A temperature independent MCD was observed, indicating an upper state degeneracy. A Fano antiresonance is observed in the absorption spectrum. No splitting was observed for the lines under uniaxial stress at 10 K. A model for these new centres is proposed.