Abstract
Emission Mössbauer spectroscopy is about three orders of magnitude more sensitive than the conventional absorption mode, thereby allowing parts per million substitution of 57Co at the Cu or Mn active site without perturbing the finely-tuned material. 57Co faithfully probes the behavior of Cu-based high temperature superconductors and mixed valence magnetoresistive manganites. The application of emission Mössbauer spectroscopy to biological systems is also highlighted.
