Mossbauer Spectroscopy at Knox College
|NEWS: This research project was presented at the spring meeting of ISAAPT at Urbana on Friday and Saturday, April 14 and 15 2000.|
Mössbauer Spectroscopy of Iron Porphyrins: Design and construction of a variable temperature experimental setup; and, experimental observations of the temperature dependence of the Mössbauer quadrupole splitting of 57Fe in heme model compounds.
The extreme vibration sensitivity of a Mössbauer experiment demands particular attention to vibration isolation methods and careful setup design. The setup we built includes a top-loading closed cycle cryostat from Cryo-Industries with variable temperature control. Since the closed cycle cryostat - like any refrigerator - creates vibrations in its cooling process, isolation for the rest of the apparatus is imperative. The mounting of the cryostat, velocity transducer, and proportional counter is the most important part of a Mössbauer experiment. With sufficient vibration isolation achieved, the experiment practically runs itself.
Mössbauer spectroscopy measures, among other parameters, the nuclear quadrupole splitting. Distortions or asymmetries of the EFG at the nucleus create this hyperfine interaction. Our goal is to observe the temperature dependence of the quadrupole splitting of 57Fe in heme model compounds from ~15ºK to 300ºK. Analysis of the obtained spectra provides insight into the electronic structure of these compounds of vital importance for modeling and understanding the behavior of metalloproteins.
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