MOSSBAUER EFFECT WITH FE57 FOLLOWING NEUTRON CAPTURE IN FE56

Mößbauer effect measurements with the 14.4 keV gamma rays of Fe57 following thermal neutron capture in Fe56 are reported. During the transition from the capture level at 7.6 MeV to the first excited state at 14.4 keV recoil energies up to 549 eV are imparted to the Fe57 nuclei. Thus the Mößbauer gamma rays are emitted by nuclei displaced from their normal lattice positions. The measurements have been performed in order to get informations about the final position of the recoiled nuclei in metallic iron and in ordered Fe-Al alloys. Mößbauer spectra of recoil atoms in metallic iron did not show any significant deviation from the spectra of atoms on normal lattice positions. In ordered FeAl alloys of CsCl structure changes in the isomer shift due to recoil effects have been found. In a Fe3Al alloy of DO3 type order additional changes in the internal magnetic field have been observed. All results are discussed in terms of possible final positions for the primary recoiled iron atoms in the lattice. © 1969 Springer-Verlag.