VIBRONIC INTENSITIES IN THE ELECTRONIC-SPECTRA OF TRANSITION-METAL COMPLEX-IONS .9. EXPERIMENTAL-STUDY OF THE RELATIVE VIBRONIC INTENSITIES IN THE 2EG-]4A2G TRANSITION OF THE MNF62- ION IN CS2SIF6

The relative intensities of about 90 of the more prominent vibronic bands in the 2E(g) --> 4A2g luminescence spectrum of the MnF6(2-) ion in Cs2SiF6 have been measured at 80 K. The reported intensities cover a range of more than 10(6). Corrected values of the important intensity ratios of the nu-3, nu-4, nu-6 vibronic origins are given as 1:4.02:5.45. Most of the features can be assigned as progressions in the nu-1, nu-2 even parity vibrational modes based on the magnetic dipole allowed electronic origin and the nu-3, nu-4, nu-6, odd parity vibronic origins, up to four members of the progressions being observed. Prominent features also include combinations of the three odd vibrational modes. Anharmonic effects are small. The intensity mechanisms of these features are briefly discussed. It is likely that second order and third order Herzberg-Teller vibronic coupling makes a significant contribution to the intensity mechanism. These data will be used in subsequent theoretical models of the intensity mechanism.