Vibronic intensities in the electronic spectra of transition metal ions

Abstract

The electric dipole vibronic intensities due to the three odd parity vibrational modes of the ⁴ A _2g → ⁴ T _1g (t ² e) transition of the octahedral complex ion MnF₆ ^2- have been evaluated using a combination of crystal field and ligand polarization methods. Several different force fields and radial functions have been employed. For the ligand polarization term, coupling of the induced ligand dipole to both the metal electric quadrupole and the electric hexadecapole are considered. Whilst the crystal field and these two ligand polarization contributions to the total vibronic intensity are all within a factor of ten, they each contribute to different vibronic origins. This shows that for this ion it is not sufficient to truncate the expansion of the metal ion electric multipole moment at the leading term.