Equipment for a Mossbauer Spectrometer

The apparatus of a Mossbauer spectrometer is not especially complicated compared with other nuclear-related spectral techniques and fundamentally consists of three parts a source, an absorber, and a detector. 

There are several types of source, e.g. Co, Sm, Gd, and Sn, which are applicable for varied samples, respectively. When probing Fe samples, the excited radioactive source Co/Rh ( Co in a rhodium matrix) decays via electron capture with emitted gamma rays at 122 and 14.4 keV with additionally imparted Doppler energy since the source moves relative to the absorber. The source under the control of a velocity transducer can move back and forth with constant velocity, sinusoidally, in a symmetric sawtooth, or any other complicated way therefore, the Doppler energy as well as the energy of gamma quanta can be modified in a controllable marmer. 

The second part of a Mossbauer spectrometer is the absorber, in which the sample resonantly absorbs the source emitted gamma rays. Part of the gamma rays are transmitted through the absorber while others are absorbed and excite the sample to re-emit gamma rays. X-rays, or electrons. 

There hence exist two modes of arrangement for the third part of the spectrometer, the detector the transmission geometry and the scattering geometry. The detector of the former counts the number of unaffected transmitted gamma rays whereas that of the latter counts that of re-emitted gamma rays. X-rays or electrons. Since the count rate, I(v), is affected by many factors as shown in the formula below  

Besides the three major parts, modern Mossbauer spectrometers, to satisfy the requirement of high count rates, also utilize a fast pre-amplifier, a multichannel analyzer (which is now generally replaced by a computer or microprocessor), a calibration system (which is normally an interferometer) and a stable cryostat (such as simple He baths, He-flow cryostats, and He/ He refrigerators) during plotting of the Mossbauer spectrum. 

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