Site symmetry of the Eu3+ ion in (Et4N)3[Eu(NCS)6]

The luminescence spectrum of (Et4N)3[Eu(NCS)6] at 77 K consists of 27 lines. They are assigned to the radiative transitions from the 5D0 and 5D1 levels to the 7Fsub(J) manifold on the basis of selective-excitation experiments. The relative intensity of forced electric and magnetic dipole transitions leads to the conclusion that the complex ion does not possess an inversion centre. Two levels are observed J=1, three (or possible four) for J=2, three for J=3 and seven J=4, which is consistent with a crystal field of tetragonal symmetry. Possible point-groups of symmetry are D4, Csub(4v), C4, Dsub(2d) and S4. Inspection of the IR and Raman spectra shows that three types of vibrations occur; IR active mode, Raman active mode, and both IR and Raman active modes. Therefore, the local symmetry of the europium (III) ion in (Et4N)3 [Eu(NCS)6)may be described as a tetragonal distortion of 0sub(h) belonging to the D4 point-group of symmetry. (author)