Crystal Field Analysis And Monte Carlo Simulation Of Lattice Disordering For Cm3+ In Ypo4 And Lupo4

A method of analyzing inhomogeneous line broadening with crystal-field theory is presented. For actinide ions with unfilled f-shells in solids, the most important contribution to line broadening of f-electron transitions is from short-range interactions with distorted lattice. Optically active curium ions are used to measure the degree of radiation damage in the vicinity of their lattice site. The radiation damage was produced by decay of distant Cm-244(3+) ions. Fluorescence line narrowing (FLN) spectra show that inhomogeneous line broadening induced by alpha-decay of the actinide ion Cm-244(3+) in single crystals of LuPO4 and YPO4 has a microscopic nature. Namely, correlation is absent between energy levels of the Cm3+ ions at different local environments. Monte Carlo simulation of lattice distortion and crystal-field calculation of Cm3+ energy levels have been conducted to provide a quantitative interpretation of the experimental results. This method should be applicable to 4f- and 3d-ions in crystalline materials with lattice distortion. [S0021-9606(00)71001-4].