Polarisation effects in Moessbauer absorption by powder samples in external magnetic fields

The polarisation dependence of the absorption cross section must generally be taken into account in calculating Moessbauer absorption spectra of powder samples if they are partly polarised by an external magnetic field. The dependence of the intensity of the absorption lines on the absorber thickness with an external field of Hsub(a)=50 kG is shown in the case of the paramagnetic specimen Fe(ClO4)2 .6H2O. The calculation procedure is described and the results are compared with the usual thickness corrections neglecting polarisation effects. (Auth.)