Determination of the electric field gradient and the magnetic field in M\"ossbauer spectrocsopy by half-cube method

This paper presents a new method to determine all components of the electric field gradient tensor and orientation of the hyperfine magnetic field axis in the absorber Cartesian frame for M"ossbauer spectroscopy for nuclear transitions between levels with spin 3/2 and 1/2. 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.