Influence of radiation damage on perturbed angular distributions: The PoPbsystem

Perturbed angular distribution measurements in a Pb target have been performed for the ${}_{}{}^{206,208,210}{}_{}{}^{}\mathrm{Po}$($8^{+}$) and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Po}$(${17/2}^{-}$) 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 $\frac{\Gamma }{2}=0.9\mathrm{}\times {10}^{17}$ V/${\mathrm{cm}}^2$ at room temperature. At higher temperatures the gradients are weaker indicating that before the measurement begins at ${10}^{-8\mathrm{}}$ sec after the implantation, some annealing of the initial damage takes place.