Electric dipole transition cross sections and effective site symmetry of Eu3+ in pseudocentric K5Eu(MoO4)4

The fluorescence and absorption spectra of Eu3+ in K5Eu(MoO4)4 have been measured at 300 K and 77 K. The fluorescence lifetime of the 5D0 state is 1.4 ms at 300 K. The largest cross section sigma(5D0→7F2(4))= 1.3x10-21cm2 and the removal of degeneracies require to replace the nearest neighbour Dsub(3d) symmetry of Eu3+ by the effective symmetries C1, C2 and Csub(s) of the whole unit cell. It is shown that C1 dominates because of the statistical distribution of K+ and Eu3+. The corresponding inhomogeneous broadening is observed at 77 K. (Auth.)