Non-Lorentzian shapes of diffusion broadened Moessbauer lines

In accordance with the calculation of Dibar-Ure and Flinn, we have observed a sharp cusp-like peak for highly broadened Moessbauer lines in bcc iron stabilized with 4 at% molybdenum. This is the first direct evidence that diffusion in bcc iron is via nearest neighbor jumps. It is also direct evidence that the angular dependence of the diffusion broadened line-width is in accordance with the theory of Singwi and Sjoelander. Possible side band resonances may be indicated near 1300sup(o)C. The experiment represents a new level of precision for diffusion Moessbauer spectroscopy, and shows the feasibility of doing high accuracy experiments of this type, using the recently developed MICE (microfoil conversion electron) detector. (orig.)