Transmission and line broadening in the Mössbauer effect. II

Abstract Calculations expressing the shape of the Mossbauer line to be expected in a transmission-type experiment are extended to the case where both emission and absorption spectra are split by a hyperfine interaction. To see the effects of spectral shape, Gaussian as well as Lorentzian spectra are considered. The results indicate that the characteristics of the transmitted line are strongly dependent upon the spectral shape. To test the calculations, the transmitted line shape was measured as a function of absorber thickness. These experiments were performed with the 14.4 keV radiation emitted by Fe 57 . To obtain unsplit spectra, Type 310 stainless steel was used for both source backing and absorbers. The observed line was more than four times as wide as the natural width, and was neither Lorentzian nor Gaussian. An unambiguous comparison with the calculations is therefore impossible. Averaging the results of analyses based on Lorentzian and Gaussian shapes yields f =67%, f ′ A =137% for those source and absorber recoilless fractions. Identically split spectra were obtained by using Armco iron for the source backing and the absorbers. In this case, the central resonance line was approximately Lorentzian. Applying the corresponding analysis yields f =67%, f ′ A =144%. These anomalously high values of f ′ A were obtained by using a conversion coefficient of15. To obtain reasonable values, a conversion coefficient of about 8 is required.