Spectra of manganese(IV) hexafluoride ion (MnF6=) in environments of <i>O</i> <i>h</i> and <i>D</i>3<i>d</i> symmetry

Abstract

The visible and near ultraviolet spectra of MnF6= have been observed in solid solutions in Cs2GeF6 and K2GeF6 in which the site symmetries of the hexafluoride ion are Oh and D3d, respectively. At liquid helium temperatures these spectra show sharp line absorption corresponding to electric and magnetic dipole transitions. The electric dipole transitions are vibronically allowed and correspond to the excitation of the three ``u'' vibrations of an octahedral, XY6 molecule. These are observed combined with the a1g completely symmetrical vibration and, we have assumed, with certain of the lattice vibrations. The assignments given for the 4A2g→2Eg and 2T1g transitions are reasonably straightforward. For the first spin allowed transition, 4A2g→4T2g, it is necessary to assume a reduction in the spin-orbit coupling parameter by a factor of about 10 to account for the observations. We have not observed the transition to the 2T2g state, and the higher lying quartet 4T1g appears as a poorly resolved progression corresponding to va1g ≈ 460 cm−1.