Electric Field Gradient at Ta in Group-IVBMetals. III.ω-Zirconium

Abstract

Using the time-differential perturbed-angular-correlation technique, we have observed the nuclear-electric-quadrupole interaction at $^{181}\mathrm{Ta}$(482 keV) as an impurity in the $\ensuremath{\omega}$-phase modification of Zr metal. The measured interaction frequencies for the two crystallographically inequivalent sites are ${\ensuremath{\nu}}_{Q}^{A}=280\ifmmode\pm\else\textpm\fi{}2$ MHz and ${\ensuremath{\nu}}_{Q}^{B}=382\ifmmode\pm\else\textpm\fi{}2$ MHz, which correspond to electric field gradients of $|e{q}^{A}|=(4.58\ifmmode\pm\else\textpm\fi{}0.19)\ifmmode\times\else\texttimes\fi{}{10}^{17}$ V/${\mathrm{cm}}^{2}$ and $|e{q}^{B}|=(6.24\ifmmode\pm\else\textpm\fi{}0.25)\ifmmode\times\else\texttimes\fi{}{10}^{17}$ V/${\mathrm{cm}}^{2}$, respectively. We find that the ratio of field gradients is in remarkably good agreement with results of a point-ion lattice-sum calculation and the gradient magnitudes support a reduced-valence picture of the $\ensuremath{\omega}$ structure.