Optical Spectra of Ru4+ in Single Crystals of K2PtCl6 and Cs2ZrCl6 at 4.2°K

The optical absorption spectra of Ru4+(4d4) has been studied at 4.2°K in single crystals of K2PtCl6 and Cs2ZrCl6. Eight electronic transitions have been observed which have a similar appearance to the spectra of OS4+(5d4) except that the vibrational structure is not as well resolved. An intermediate-coupling crystalfield analysis for a d4 configuration fits the observed electronic transitions with the parameters B = 803 cm−1, C = 1363 cm−1, Dq = 1892 cm−1, and λ4d = 1044 cm−1. The rms deviation of the energies is 262 cm−1. The observed absorptions are assigned on the basis of calculated transition probabilities and energy level diagrams. The relative linewidths are in qualitative agreement with the calculated results for a small tetragonal distortion of the cubic field. The molar susceptibility which is calculated from the optical data is in agreement with the experimental magnetic susceptibility. The calculated g values are tabulated for all the assigned electronic states. A discussion of several unassigned transitions with E > 26 000 cm−1 is given.