EU3-3)(3)F-4( AS A LOCAL PROBE TO CHARACTERIZE THE STRUCTURE OF ACENTRIC K4EU2(CO)

The optical study of the trivalent europium ion in polycrystalline K4E u2(CO3)(3)F-4 is reported. Three main low symmetry sites for Eu3+ are deduced from the emission spectra at 4.2 K. Extra lines are also prese nt at low temperature, which may be assigned to a fourth site. When th e temperature increases, these extra lines disappear without energy ch ange of other lines. This reversible phenomenon is not yet explained. Above 8 K, site to site energy transfer becomes effective. The electro static crystal field effects on the F-7 multiplet are also evaluated o n the basis of the phenomenological crystal field theory. (C) 1998 Els evier Science S.A.