Jahn‐Teller Effect on Excited Orbital Triplet States of 3d n Ions in Eightfold Cubic Coordination. Co 2+ and Fe 2+ in CdF 2

The ions Co 2+ and Fe 2+ can be substitutionally incorporated on Cd 2+ sites in CdF 2 . The optical absorption bands of the transitions 4 A 2g → 4 T 1g (F), → 4 T 1g (P) and 5 E g → 5 T 2g are no single bands but exhibit a pronounced triplet structure measured up to 500 K. The splittings increase linearly with \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt T $\end{document} at high temperatures. These results are explained as due to a strong dynamical Jahn‐Teller effect (interaction with τ 2g modes) on the excited orbital triplet states based on the theory by Toyozawa and Inone [3]. The frequencies of the τ 2g modes and the coupling constants (Jahn‐Teller energies) are determined. The doublet structure of the 4 A 2g → 4 T 2g absorption band and additional fine structures of the → 4 T 1g (F) band at low temperatures are discussed as probably being caused by the simultaneous action of first order spin‐orbit coupling and strong T ⊗ τ 2g coupling.