Reason for line broadening in emission Mossbauer spectra

Resonant lines observed in source experiments are usually significantly broader thanthosein the corresponding absorber experiments. In order to explain this phenomenon, the model of a trapped electron has been proposed. Auger electrons emitted, for instance, after electron capture by Co-57 or after the converted isomeric transition of Sn-119m, as well as secondary electrons, may be trapped in the vicinity of the nucleogenic ion. An asymmetric distribution of quadrupole splittings in the resulting emission Mossbauer spectra is thus a consequence of electron capture by lattice traps located at different distances from the daughter ion. Estimates of quadrupole splitting values, which may be causedby trapped electrons located at different distances from the nucleogenic atom, support the above mentioned model.