Abstract
Problem of unambiguous determination of all components of the electric field gradient and hyperfine magnetic field in case of mixed hyperfine interaction was solved for the first time. Concept of a new method to determine orientation of hyperfine fields in the absorber Cartesian frame for Mössbauer spectroscopy for nuclear transitions between levels with spin 3/2 and 1/2 is presented. The method can be applied for single-crystal absorbers with well separated absorption lines in their spectra. Explicit formulas derived from velocity moments are presented. The new method allows full separation of the electric quadrupolar and magnetic dipolar hyperfine interactions by using unpolarized radiation.
Highlights
Determining the hyperfine parameters from the Mossbauer spectrum has been widely discussed in the literature, and it is known that all parameters cannot be determined from a spectra of texture-free samples [1,2]
We show that all components of the electric field gradient and orientation of the hmf axis can be determined from measurements on a single crystal with a few different directions of the wave vector of the photon with respect to the absorber frame
We briefly present some earlier results related to the intensity tensor, velocity moments, and invariants used in this study
Summary
Determining the hyperfine parameters from the Mossbauer spectrum has been widely discussed in the literature, and it is known that all parameters cannot be determined from a spectra of texture-free samples [1,2]. We show that all components of the electric field gradient (efg) and orientation of the hmf axis can be determined from measurements on a single crystal with a few different directions of the wave vector of the photon with respect to the absorber frame. By three measurements of mγ, with circularly polarized radiation and with γ parallel to x, y, and z axes defining Cartesian coordinates in the absorber frame, we determine three components of vector m. Because V (k) = ek ⊗ ek, where ek (k=x,y,z) is an orthonormal basis in which V is diagonal, the components of V (k) operator determined in the absorber basis can be solved in the manner given in (11) to obtain explicit vectors forming PAS of the efg. Equation (16) works for a nondegenerate case, that is, one were all three eigenvalues are different. These considerations are consistent with group theory arguments and with the concept of magic angle measurements [12,13]
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