CHANGE IN NUCLEAR RADIUS UPON EXCITATION FOR $sup 119$Sn, $sup 121$Sb, $sup 125$Te, $sup 127$ $sup 129$I, AND $sup 129$Xe FROM MOESSBAUER ISOMER SHIFTS.

The ratio $\frac{\ensuremath{\delta}〈{R}^{2}〉}{〈{R}^{2}〉}$ for two nuclei can be obtained by comparing the measured isomer shifts for isoelectronic compounds of the two elements. Such a determination is fairly insensitive to the absolute value of the electron density at the nucleus. These ratios have been found sequentially for $^{119}\mathrm{Sn}$, $^{121}\mathrm{Sb}$, $^{125}\mathrm{Te}$, $^{127,129}\mathrm{I}$, and $^{129}\mathrm{Xe}$. Taking $\frac{\ensuremath{\delta}〈{R}^{2}〉}{〈{R}^{2}〉}$ for $^{119}\mathrm{Sn}$ to be 2.4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$, absolute values of $\frac{\ensuremath{\delta}〈{R}^{2}〉}{〈{R}^{2}〉}$ for remaining nuclei have been found. The values are -14.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$, 1.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$, -4.8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$, 6.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$, and 0.55\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ for $^{121}\mathrm{Sb}$, $^{125}\mathrm{Te}$, $^{127}\mathrm{I}$, $^{129}\mathrm{I}$, and $^{129}\mathrm{Xe}$, respectively. These values overlap those obtained directly by our electron-density calibrations, done individually, although they are different in some cases from earlier determinations. These results also supply a consistent set of values for the isomer shift per $5p$ or $5s$ electron for all five elements.