Excited state properties of ferrate(VI) doped crystals of K2SO4 and K2CrO4

The 15 K polarized single-crystal absorption spectra of Fe6+ doped K2SO4 consist of two sharp bands below 10 000 cm(-1) assigned to the spin-flip transitions (3)A(2) --> (1)E, (1)A(1) and a series of broad bands in the near-infrared (NIR) and visible region assigned to (3)A(2) --> T-3(2), T-3(1) d --> d transitions and O --> Fe charge transfer transitions. From the excited state absorption (ESA) spectrum we derive that the T-1(2) state lies 19 300 cm(-1) above the (3)A(2) ground state. This allows a clear assignment of all the ligand field states below 33 000 cm(-1), which is in good agreement with an angular overlap model (AOM) calculation. Differences in the temperature dependence of the (1)E --> (3)A(2) luminescence intensity upon broadband and (3)A(2) --> (1)A(1) excitation are shown to be due to direct nonradiative relaxation processes from T-3(2) to the (3)A(2) ground state.