抄録
The splitting of the ground state of Fe57 in iron corresponds to 2.2 millidegrees. At a very low temperature, the population in the m=-1/2 level will become greater than that in the m=+1/2. For an iron absorber, the ratio of the intensities of transitions arising from the m=-1/2 level to those from the m=+1/2 level is increased as the temperature approaches to 2.2 millidegrees.
Utilizing this effect, we have measured the temperature of an iron absorber to be 7.9 millidegrees without any ambiguity of depolarization effects through β decay, which might be experienced in the Mössbauer Effect thermometer with the source kept at very low temperature.
