Mössbauer-effect measurements have been carried out to investigate the influence of ${\beta }^{-}$ decay and $K$ capture on the electronic structure of the decaying atom. Sources of ${\mathrm{I}}^{125}$ in NaI${\mathrm{O}}_3$ and NaI${\mathrm{O}}_4$ showed multiple-line spectra. It was found that through the $K$ capture and the subsequent processes the bonding of the iodine atom is uncoupled and the resulting tellurium atom forms new types of bonds. Sources of ${\mathrm{Sb}}^{125}$ in NaSb${\mathrm{O}}_3$ and ${\mathrm{Sb}}_2$${\mathrm{O}}_3$ exhibited single-line spectra and no evidence for multiple lines was found, which is interpreted as indicating a smaller distortion of the electron shell through ${\beta }^{-}$ decay. The Mössbauer effect of the 57.6-keV transition to the ground state of ${\mathrm{I}}^{127}$, which follows the ${\beta }^{-}$ decay of the ${\mathrm{Te}}^{127m}$, was used to measure the isomer shift of various iodine compounds at 4.2°K. The linewidths and quadrupole splittings of these compounds were determined in order to check the microscopic stoichiometry, because the same compounds containing ${\mathrm{I}}^{125}$ were then used as sources against a single-line absorber. The isomer-shift scale was calibrated in terms of $s$-, $p$-, and sometimes $d$-electron shielding, according to the atomic configuration and hybridization, respectively. Together with the $s$-electron density of the filled $n=5\mathrm{}$ shell, calculated from the Fermi-Segré formula, a value of $\frac{\Delta R}{R}=-2.8\mathrm{}\times {10}^{-5\mathrm{}}$ was obtained for ${\mathrm{I}}^{127}$. The 35.5-keV transition in ${\mathrm{Te}}^{125}$ was used to measure the isomer shift and quadrupole splitting of a variety of tellurium compounds at 78°K. A linear relation is found between the isomer shifts of analogous iodine and tellurium compounds, confirming that isoelectronic structures are formed by these elements. Applying the same procedure for the isomer-shift scale calibration as for iodine, $\frac{\Delta R}{R}=+2.4\mathrm{}\times {10}^{-5\mathrm{}}$ is derived for ${\mathrm{Te}}^{125}$.

• Received 27 June 1968

DOI:https://doi.org/10.1103/PhysRev.175.512