Thermometry nuclear orientation

Fig. 9.17. Energy level diagrams for 54Mn and 60Co (slightly simplified). These are the two decay favourite schemes used for nuclear orientation thermometry.

Gamma-ray anisotropy or nuclear orientation thermometry OOl-l Spatial distribution of gamma-ray emission Spatial distribution related to Boltzmann factor for nuclear spin states Useful standard forT < IK... 

Nuclear orientation thermometry depends on the anisotropic emission of y-rays from polarized radioactive nuclei. The extent of the anisotropy is detemined by the degree of polarization which, in turn, varies inversely with the absolute temperature. Since the nuclear hyperfine splittings are usually known to high precision, the thermometer is in principle absolute and does not require calibration. The useful temperature range is relatively narrow, however, being limited by radioactive self-heating at the lower end and insensitivity at the upper end. 

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