Mouml;ssbauer Studies of Iron Organometallic Complexes. IV. Sign of the Electrichyphen;Field Gradient in Ferrocene

摘要

The quadrupole splitting of57Fe Mouml;ssbauer spectra gives the magnitude, but not the sign, of the electrichyphen;field gradient. The sign can be determined by magnetically perturbing the energy levels, such that one line splits into a triplet and the other line splits into a doublet. A firsthyphen;order perturbation treatment for the axially symmetric electrichyphen;field gradient case is given for powdered samples. The method is applied to ferrocene, which has been the subject of many theoretical papers. A crystalhyphen;field treatment predicts a positive efg, and molecular orbital treatments predict negative efg's. At 40 kG applied, the two lines split clearly into a doublet and a triplet. The result agrees with the MO treatment. This also explains the essential vanishing of the efg in ferrocinium compounds.