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

Abstract

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-$\ensuremath{\gamma}$ 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.NUCLEAR REACTIONS (HI Coulomb excitation) $^{186}\mathrm{W}$, $E(^{16}\mathrm{O})=40$ MeV, $E(^{32}\mathrm{S})=80$ MeV, recoil Gd single crystal; measured $^{16}\mathrm{O}\ensuremath{\gamma}(\ensuremath{\theta})$, $^{32}\mathrm{S}\ensuremath{\gamma}(\ensuremath{\theta})$; deduced sign $^{186}\mathrm{W}$(2+) quadrupole interaction. $^{180}\mathrm{Hf}$, $E(^{16}\mathrm{O})=40$ MeV, recoil Hf single crystal; measured $^{16}\mathrm{O}\ensuremath{\gamma}(\ensuremath{\theta})$; deduced sign $^{180}\mathrm{Hf}$(2+) quadrupole interaction.