CCZO -- Soil Geochemistry -- Mössbauer spectroscopy -- Calhoun CZO -- (2015-2015)

Soil samples analyzed via Mössbauer spectroscopy at three temperatures (295K, 77K and 4.2K). In each case the sample is loaded into the machine without prior modification (no grinding) to an ideal thickness based on the amount of iron in the sample. Transmission 57Fe Mössbauer spectroscopy was performed with a variable temperature He-cooled system with a 1024 channel detector. A 57Co source (~50 mCi) embedded in a Rh matrix was used at room temperature. Samples were mounted between two pieces of 0.127 mm thickness Kapton tape. In some cases, this was done inside an anoxic glovebox, and transferred immediately to the spectrometer cryostat to avoid sample oxidation prior to analysis. In other cases dried samples were used. The velocity (i.e., gamma-ray energy) was calibrated using α-Fe foil at 298 K. The transducer was operated in constant acceleration mode and folding was performed against the calibrated Fe foil to achieve a flat background. The raw sample files here are folded spectra using the most recent collected calibration standard. Data collection times are typically 24 h per sample per temperature, however can be longer/shorter in samples with less/more iron concentration.