Resonance Detectors for Mössbauer Experiments

The Mössbauer effect can be observed by detecting the gamma rays or the internal-conversion electrons and X-rays that are emitted in the de-excitation of nuclei excited previously by the resonance absorption of gamma rays. The use of conversion electrons for recording the resonance absorption is limited by the short range of these electrons. However, in special detectors--gas proportional and thin plastic scintillators--where the absorber is an integral part of the device, the detection can be made quite efficiently. In this paper the properties (counting efficiency, background, and line shape) of these resonance detectors will be discussed and compared with experimental data. It will be shown that in certain geometrical configurations the line width can be reduced whereas its shape remains very close to the Lorentzian. The detector used in this experiment is a flat gasflow proportional detector in which the cathode surface is coated with iron enriched in the isotope Fe57. The relative merits of the different detection systems will be discussed briefly.