HYPERFINE STRUCTURE MEASUREMENTS ON ANHYDROUS IRON HALIDES WITH MOSSBAUER EFFECT

Mössbauer effect measurements were performed with the anhydrous iron halides FeCl2, FeBr2 and FeI2 at 78° K and 4 K° and with FeCl3 at 4 °K. The quadrupole splitting, the isomer shift and the magnetic field at the nucleus were determined. From the quadrupole splitting it follows that in FeCl2, FeBr2 and FeI2 the ground state is a doublet and that the singulet in these compounds is separated from it by (145±35) cm-1, (175±35) cm-1 and (135±35) cm-1 respectively. The isomer shift shows the presence of strong covalence effects in all compounds. The large isomer shift in FeBr2 cannot be fully explained. From the isomer shift and the magnetic field at the nucleus in FeCl3 it can be concluded that the Fe+++ ions has an 3 d5,6 4 s0,45 configuration. In FeCl2, FeBr2 and FeI2 the smallness of the magnetic field can be explained by a not fully quenched orbital angular momentum of 0.6<Lz<1. © 1968 Springer-Verlag.