Evaluation of the Fe2+/Fe3+ ratio from57Co Mössbauer emission spectra: Influence of the relaxation of Fe3+

The Fe3+ fraction after the EC of57Co is usually evaluated supposing that ferric ions contribute a quadrupole doublet to Mossbauer emission spectra. It is shown that a not sufficiently fast relaxation of the electron spins may falsify the evaluated intensity even by a factor 2. Additional information can be gained from measurements performed in a large velocity span at low temperatures in high magnetic fields.