The 5d←4fexcited states of [Ce(OH2)9]3+

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Abstract
Five absorption bands of the allowed 5d←4f transitions of Ce3+ were detected in the ultraviolet region between 37 and 51 × 103 cm-1 by σ- and π-polarized absorption, luminescence excitation, and MCD spectra with the single crystals of Ce3+ doped lanthanum ethylsulphate enneahydrate. In the crystal, Ce3+ is in a D 3h ligand field of nine water molecules such as in [Ce(OH2)9]3+. Two resolved luminescence bands detected in 30 and 32 × 103 cm-1 at liquid nitrogen temperature are assigned to the transitions to the 2 F 5/2 and 2 F 7/2 substates of the ground 2 F(4f 1) state split by the spin-orbit coupling of a cerium 4f electron. On the other hand, the five absorption bands are assigned to five Kramers doublets of excited 2 D (5d 1) state split by the ligand-field interaction and the spin-orbit coupling of a cerium 5d electron. A greater Stokes shift between absorption and emission maxima observed in the crystal indicates a destabilization of the coordination bonds in the excited state.