Cryostats for Mössbauer Experiments

Abstract

There may be several reasons for needing low temperatures in a Mössbauer experiment. First, the fraction f of gamma rays, emitted or absorbed without recoil energy loss, increases with decreasing temperatures and actually only a few of the possible transitions (see, for instance, Boyle and Hall [1]) will show an appreciable Mössbauer effect at room temperatures. Second, the sample material under investigation may show characteristic properties, for example, magnetic ordering (see Wertheim [2]) only at low temperatures. Third, many measurements, such as a precise determination of the isomer shift, require that source and absorber be kept at a constant and readily reproducible temperature. This requirement is comparatively easily achieved by keeping the sample at the boiling point of a liquefied gas, usually liquid nitrogen (see, for example Preston et al. [3]).