Study of liquid diffusion by M ssbauer absorption and Rayleigh scattering

Abstract

Mossbauer experiments have been performed using ⁵⁷Co as source and a solution of ferric and ferrous sulphate in glycerol as resonant absorber. From the diffusive line broadening, the existence of `jump' diffusion of the Fe<sup>3+</sup> ions is inferred, and estimated to be about three times greater than the `continuous'-type diffusion at 0 °C. On the assumption of a theoretical model for diffusion, the mean square displacement of the diffusing ions is deduced as a function of time, and indicates a diffusion coefficient varying with time at short times. Possible explanations are suggested. Further experiments have been performed using a conventional stainless steel absorber, but observing the radiation scattered by liquid glycerol. Diffusive line broadening is again observed, but the firmness of the conclusions drawn is limited by unavoidably low experimental accuracy. These conclusions concerning the diffusion mechanism are, however, in general agreement with the absorption experiments. The results are discussed in the light of the general theory of de Gennes for the mean square width of the broadened line.