Crystal-field splitting, magnetic interaction, and vibronic excitations of 244Cm3+ in YPO4 and LuPO4

The electronic and lattice-dynamical properties of 244Cm3+ doped orthophosphate crystals of YPO4 and LuPO4 were studied using site-selective fluorescence line narrowing (FLN) techniques. Although radiation damage caused substantial inhomogeneous line broadening, FLN gave rise to sharp resonant and satellite lines. Samples were annealed at 500 degree C to eliminate satellite lines due to Cm3+ ions at different lattice environments. The crystal- field splitting of the nominal 8S7/2 ground state and the 6D7/2 excited state was determined from an analysis of the excitation and fluorescence spectra using an exchange charge model of crystal field interaction within the scheme of intermediate coupling. The effective g factors of the four Kramers doublets of the J=7/2 ground state and the lowest doublet of the excited state were evaluated from a least-squares fit of the observed Zeeman splitting to an effective-operator Hamiltonian. The energies of phonon modes were estimated from the observed vibronic spectra of the 244Cm3+ ion in both hosts and compared with the results of previous optical and neutron measurements. copyright 1998 American Institute of Physics