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

The optical spectra of Os⁴⁺ ${\text{(5d}}^4)$ 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 $d^4$ manifold fits the observed ten electronic, 0–0 transitions with an rms deviation of 228 cm⁻¹ for the parameters $\text{A\hspace{0.17em}=\hspace{0.17em}0, B\hspace{0.17em}=\hspace{0.17em}741, C\hspace{0.17em}=\hspace{0.17em}1296, V\hspace{0.17em}=\hspace{0.17em}22490}$ , and ${\lambda }_{\text{5d}}\text{\hspace{0.17em}=\hspace{0.17em}2416}{\mathrm{cm}}^{\text{−1}}$ . 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 $t_{\text{2g}}^4{\mathrm{\hspace{0.17em}\to \hspace{0.17em}t}}_{\text{2g}}^3{e}_g$ 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 $\text{5d}$ systems are presented.