Optical Spectra of Os4+ in Single Cubic Crystals at 4.2°K

The optical spectra of Os4+ (5d4) in single cubic crystals of K2PtCl6, Cs2ZrCl6, Cs2HfCl6, and Rb2ZrCl6 at 4.2°K has been studied. The spectrum is characterized by very narrow lines in the region from 10 000–36 000 cm−1. Vibrational structure is observed which may be assigned to the ungerade modes of the OsCl62− complex in the lattice. A crystal-field analysis within the d4 manifold fits the observed ten electronic, 0–0 transitions with an rms deviation of 228 cm−1 for the parameters A = 0, B = 741, C = 1296, V = 22490, and λ5d = 2416 cm−1. The calculated molar magnetic susceptibility agrees with that found for concentrated crystals such as K2OsCl6 and Cs2OsCl6. The analysis of the electronic states was dependent upon a calculation of intensities for the t2g4 → t2g3eg transitions. The calculated results are given for a tetragonal distortion of the cubic field and are shown to qualitatively agree with the linewidth of the transitions. The calculated g values for all observed transitions are tabulated. Finally, several conclusions about the optical spectra of 5d systems are presented.