Influence of radiation damage on perturbed angular distributions: The Po<i>Pb</i>system

Abstract

Perturbed angular distribution measurements in a Pb target have been performed for the $^{206,208,210}\mathrm{Po}$(${8}^{+}$) and $^{209}\mathrm{Po}$(${17/2}^{\ensuremath{-}}$) isomeric levels. Target temperatures were varied from 80 to 575 K and magnetic fields were applied from 0.1 to 6.1 T. The data can be explained with a combined strong magnetic and weak quadrupole interaction, with the quadrupole interaction arising from radiation damage in the host correlated in position with the implanted ion. A perturbation theory treatment of the combined magnetic and quadrupole interaction was developed and provides the basis for the interpretation of the results. The data are consistent with a Lorentzian distribution of electric field gradients centered around zero with half width $\frac{\ensuremath{\Gamma}}{2}=0.9\ifmmode\times\else\texttimes\fi{}{10}^{17}$ V/${\mathrm{cm}}^{2}$ at room temperature. At higher temperatures the gradients are weaker indicating that before the measurement begins at ${10}^{\ensuremath{-}8}$ sec after the implantation, some annealing of the initial damage takes place.NUCLEAR REACTIONS $^{204,206,207,208}\mathrm{Pb}(\ensuremath{\alpha},2n)^{206,208,209,210}\mathrm{Po}^{*}$, $E=24\ensuremath{-}25.5$ MeV. Enriched targets measured $\ensuremath{\sigma}({E}_{\ensuremath{\gamma}};\ensuremath{\theta},H,t,T)$ for isomeric levels. Deduced electric field gradients from radiation damage.