Abstract
The theory of the intensity of vibronically allowed electric dipole transitions for octahedral complexes is investigated. The calculation is carried out within the confines of ligand fieldtheory and full account is taken of spin–orbit coupling. Of particular interest are those transitions which take place with a considerable change of internuclear configuration and which may be characterized as mainly involving a tn2g→tn−12gegt2gn → t2gn−1eg transition. Certain selection rules are determined and an approximate two‐parameter form is found for the intensity of the allowed transitions. This calculation is particularly useful as an aid in assigning transitions in regions where there are many possible states. Application is made to the low‐temperature optical spectra of Os4+ and of Re4+ in single crystals of Cs2ZrCl6. The spectra of OsF6 are also discussed. Some predictions are made about the low‐temperature optical spectra of W4+, Ir4+, and Pt4+ in single crystals of Cs2ZrCl6.