Abstract
The K absorption spectra of sulfur in FeS, FeS2 (pyrite), and Fe2S3 have been measured with a 50 cm bent‐quartz‐crystal vacuum spectrograph. The spectra of FeS and Fe2S3 are similar to each other but are fairly different from that of FeS2. The FeS2 spectrum is discussed in terms of two theoretical calculations: the energy band for FeS2 (pyrite) and the molecular orbital (MO) of the S22− ion. The spectra for FeS and Fe2S3 are explained by the application of Terakura’s theory and the first absorption band is attributed to the transitions to the empty antibonding states formed by the redistribution of the sulfur 3p bands under the influence of the iron 3d bands.