Fe-57 Emission Mossbauer Study of Recoil and Auger After-effects in Ni-57 Labeled Knif3

Devillers, Michel [UCL] Ladrière, Jean [UCL] Apers, Désiré [UCL]

The chemical after-effects associated with the radioactive sequence Ni-57 --> Co-57 --> Fe-57 are investigated by means of Fe-57 emission Mossbauer spectroscopy in Ni-57-labelled KNiF3. The results are interpreted by comparing with previously reported data on the corresponding Co-57-doped compound. In agreement with the energetics of the Ni-57 decay scheme, recoil of nucleogenic Co-57 atoms during the first transition has been detected in Ni-57:KNiF3 samples stored at 77 K. Annealing at room temperature results in partial healing, temperatures around 400 K being required to achieve total recovery of the lattice. Unequivocal confirmation is provided for the preferential stabilization of the nucleogenic Fe-57 atoms in the tervalent state in nickel compounds.