Anthony Kremin and Josh Resch
University of Minnesota
Methods of Experimental Physics Spring 2012
In this experiment we used Mössbauer spectroscopy to measure the isomer shift, Zeeman splitting, and quadrupole interaction for 57Fe Foil, a-Fe2O3, and Fe3O4 through recoilless absorption of a photon. The recoilless emission of gamma rays from a 5mCi radioactive source of 57Co allowed it to emit 14.4keV gamma rays with a precision on the order of 10-9 eV. This resolution is smaller than the hyperfine transition energies of the iron nuclei by more than a factor of 10. By oscillating the 57Co source by mm/sec, toward and away from the iron compound, we were able to Doppler shift the emitted 14.4keV gamma ray by several 10-8 eV, and create varying energies that formed a distribution centered around 14.4keV, which were used to measure the absorption energies due to the hyperfine energy structure of iron. The energies were determined by decreased counts at measured Doppler velocities. All calculated quantities were found to be within the uncertainties of our experiment and that of the literature, with the exception of the ground state Zeeman splitting of a-Fe2O3, the average excited state Zeeman splitting of Fe3O4, and the average isomer shift ofFe3O4? at room temperature.