Mössbauer Effect of the Second Excited State ofFe57

The Mössbauer effect of the 136.4-keV decay of the second excited state of ${\mathrm{Fe}}^{57}$ has been observed using a new scattering technique. The decay of the second excited state following resonant absorption to the first excited state was detected. A 6-mg/${\mathrm{cm}}^2$ ${\mathrm{Fe}}^{57}$ scatterer was used. The Mössbauer effect was unambiguously observed using 15 mCi of ${\mathrm{Co}}^{57}$ diffused into an iron host lattice as a source. With both source and scatterer at liquid-helium temperature, the recoilles fraction for an iron host lattice was estimated to be approximately 2×${10}^{-3\mathrm{}}$. Partially resolved magnetic hyperfine structure was observed using a 15-mCi source of ${\mathrm{Co}}^{57}$ diffused into palladium. Since the structure was only partially resolved, the sign of the magnetic moment was not determined with certainty. However, the assumption that the magnetic moment is negative led to agreement with the magnitude of the magnetic moment previously reported by Körner. The gyromagnetic ratio that was determined was $g=-0.39\mathrm{}\pm 0.04$.