Temperature Dependence of theβ-Tin Isomer Shift

A study of the Mössbauer spectrum of $\beta$-tin from 77 to 450°K shows that the isomer shift exhibits an explicit dependence on temperature, and therefore that the electron density at the nucleus depends on temperature even when the volume is held constant. Plausible arguments are presented to show that this effect is related to the explicit temperature dependence of the Knight shift. By combining Knight-shift and Mössbauer results, it is found unambiguously that in ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$, $\frac{\delta R}{R}$ is positive and equals (1.8±0.4) × ${10}^{-4\mathrm{}}$.