Nuclear Quadrupole Precession After Recoil Implantation into Single Crystals forHf180in Hf andW186in Gd

Coulomb excitation with ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ beams was used to excite, polarize, and implant ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$(2+) in Hf single crystals and ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$(2+) in Gd single crystals. Particle-$\gamma$ correlations for different crystal orientations were measured. The general features of the perturbed correlations were consistent with the prediction for a static axially symmetric quadrupole interaction in a single crystal, but additional perturbations had to be taken into account to explain the results quantitatively. Special experimental geometries were employed to separate these perturbations. In the ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$ in Hf experiment the sign of the quadrupole interaction could be unambiguously determined as negative using the known polarization of the excited nucleus. In the ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$ in Gd case unknown perturbation mechanisms reduced the terms linear in the quadrupole interaction frequency to such an extent that the negative sign indicated is less certain. Control experiments with implantation of ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$ in Cu foils were used to check the experimental technique for systematic errors.