TRENDS IN MOSSBAUER POLARIMETRY WITH CIRCULARLY POLARIZED RADIATION Mossbauer polarimetry

摘要

In Mossbauer Spectroscopy (MS) the use of circularly polarised radiation adds new capabilities not available in conventional MS. The resonant absorption becomes dependent on the relative orientation of the photon angular momentum and direction of the hyperfme magnetic field acting on the nucleus. In complex systems, either with mixed hyperfme interactions or chemical or magnetic disorder, this new option allows one to determine magnetic structure of such systems in complementary way to the neutron diffraction. Sometimes its sensitivity to the Moessbauer nucleus leads to the unique possibility of identifying individual contributions of various species to the net magnetisation. The formalism of so-called velocity moments for the I=3/2→1/2 nuclear transitions permits one to extract some averages of hyperfme fields irrespective of the type of the interactions and eventual shape of their distribution. The applicability of the method is presented for a number of experimental situations. Construction of the source used in these experiments is also presented.