Hyperfine fields at the Fe57 nucleus in monovalent iron (D6, 3d64s) isolated in solid xenon

The Mössbauer effect was used to unequivocably identify and measure the effective internal magnetic field at the Fe57 nucleus in monovalent iron in its D6, 3d64s state isolated in a xenon matrix. The monovalent iron was produced by depositing the iron atoms in a matrix doped with HI and the subsequent electron transfer between the electron donor (Fe0) and the acceptor species promoted by photoexcitation. For an applied external field of 28 KOe, an induced anisotropic magnetic hyperfine field at the Fe57 nucleus was measured with Hz=350±10 kOe and Hx=700±10 kOe. The ground-state Kramers doublet was uniquely determined from the value of both the magnetic hyperfine field and the quadrupole splitting, using a crystal-field-theory analysis and results of ab initio spin-polarized Hartree-Fock calculations for the 3d64s1(D6) and 3d64s1(D4) terms of monovalent iron. The agreement between theory and experiment was found to be excellent. A systematic study of the possible molecular compounds in the Fe-Xe (HI) mixtures was carried out. For high HI concentrations FeI2 and FeI3 were observed. For low iron concentrations and 1% HI in xenon only, the monovalent iron ion was observed after photodissociation of HI.