Absorption Spectra of Ferric Iron-Containing Oxides

Abstract

The interpretation of the absorption spectra of the ferric iron‐containing oxides is extended and clarified. Largely on the basis of existing data it is shown that the majority of the discrete absorptions can be related to energy differences obtained from (cubic) crystal field calculations applied to Fe³⁺ provided a reduction of the ⁶S—⁴G separation (relative to the free ion value) is first introduced. The strong, continuous absorption which characteristically obscures the region above 20 000 cm^—1 in the undiluted ferric oxides is assigned to charge transfer transitions. One low‐energy absorption band (not characteristic of the iron oxides) found in the spectrum of lithium ferrite is tentatively assigned as the photoionization of a charged anion vacancy.