Mössbauer-Effect Studies onKr83in Bromide and Bromate Crystals

Abstract

Mössbauer-effect studies have been performed using ${\mathrm{Kr}}^{83}$ sources produced by the ${\beta }^{-}$ decay of ${\mathrm{Br}}^{83}$ ($T_{\frac{1}{2}}=2.4\mathrm{}\mathrm{h}$) in various bromine compounds. Experiments were done with LiBr, NaBr, KBr, CsBr, N${\mathrm{H}}_4$Br, KBr${\mathrm{O}}_3$, and $\mathrm{K}\mathrm{r}-\beta$-hydroquinone sources at 90°K using solid krypton absorber at 22°K. No isomer shift was observed for any of the sources, indicating that the Kr outer configuration is not perturbed by the induced dipole interaction with its neighbors. No "Kr${\mathrm{O}}_3$" species was detected as a result of the ${\beta }^{-}$ decay of Br in KBr${\mathrm{O}}_3$. Broad and symmetric emission lines were observed for the Kr-hydroquinone, the bromides, and the bromate, increasing in broadening in that order. This broadening has been explained on the basis of the formation of a local distorted crystalline field, as a consequence of the internal-conversion process of ${\mathrm{Kr}}^{83m}$. From the fact that a symmetric line is observed, it has been concluded that at least two modes of distortion are formed in such a way as to produce opposite signs of the electric field gradient. The Debye temperature calculated for the alkali-bromide sources was found to be 60°K in average, and for that of H${\mathrm{N}}_4$Br a value of 90°K was derived. The techniques of source preparation and of the krypton absorber deposition are described.