Mössbauer Determination of the Debye-Waller Factor in Single-Crystal Absorbers

The equation which must be used to obtain the Debye-Waller factor f^' from M\"ossbauer absorption measurements on single-crystal samples with resolved and hence generally polarized lines is given. The polarization terms for a crystal having the symmetry of siderite are explicitly presented and theoretical area ratios are compared with recently reported values calculated from a theory neglecting polarization. New experimental data indicate that f^'>~0.6 for all directions in siderite.