On the Multipole Character of the X‐Ray Transitions in the Pre‐Edge Structure of Fe K Absorption Spectra. An Experimental Study

The K absorption edge of pure Fe and the pre‐edge Fe K absorption of FeS 2 (pyrite), Fe 2 O 3 (hematite), and FeCO 3 (siderite) are investigated with single crystal absorbers of these materials using linearly polarized synchrotron X‐radiation. From the angular dependence of the pre‐edge K absorption the existence of predominantly ligand‐field‐induced dipole transition in Fe 2 O 3 and of quadrupole transitions in FeCO 3 is concluded. The multipole character and the mechanism of the pre‐edge K absorption are discussed.