Quantitative Test of the Vibrational Anisotropy Origin of the Asymmetry of Quadrupole Mössbauer Doublets

The comparison of quadrupole doublets of M\"ossbauer spectra for monocrystals of siderite at various orientation angles and those for polycrystalline siderite gives quantitative proof of the vibrational anisotropy origin of integral asymmetry of doublets in polycrystals. Such comparison has also been used for determination of the absolute probability of the M\"ossbauer effect and of the sign of the electric field gradient on iron nuclei in siderite (which was found to be positive).