A high-sensitivity Mössbauer spectrometer facilitates the study of iron proteins at natural abundance

A Wide-Angle Mössbauer Spectrometer has been constructed, tested and shown to have approximately ten times the sensitivity of a standard Mössbauer spectrometer. The most innovative feature of the spectrometer is the eighty degree, conical acceptance geometry of its gamma-ray detector, which is constructed of 77 argon gas proportional counters with their associated charge-sensitive preamplifiers and single channel analyzers. The spectrometer has demonstrated the following features: (1) it has approximately 100 times the countrate of most existing Mössbauer spectrometers; (2) velocities reproduce to an accuracy of ±0.005 mm/s over periods of several weeks; (3) the temperatures of the source and the sample are regulated with an accuracy of ±0.1°C in the range of 4.2 to 300 K. By obtaining a high quality Mössbauer spectrum of un-enriched 0.3 mM K ₃Fe(CN) ₆, we have shown that the study of high molecular weight natural abundance iron proteins can be greatly facilitated by this spectrometer.