A SINGLE-CRYSTAL, LINEARLY POLARIZED FE 2P X-RAY-ABSORPTION STUDY OF GILLESPITE

The Fe 2p X-ray absorption spectra of single crystal gillespite, BaFeS i4O10, show a strong linear dichroism, i.e. a large difference in the absorption when measured with the polarization of the X-rays either pa rallel or perpendicular to the plane of the FeO4 group. The isotropic spectrum, obtained from measurement at the 'magic angle', and the pola rization dependent spectra have been compared to atomic multiplet calc ulations and show an excellent agreement with theory. Analysis of the branching ratio, the linear dichroism, and the detailed peak structure confirms that the (5)A(1) level is the ground state at room temperatu re and pressure. The B-5(2) level is sufficiently low in energy that a distortion of the electronic charge density, induced by increased pre ssure, may result in a B-5(2) ground state.