Sensitive Probing of Surfaces by Electric Quadrupole Interaction Demonstrated for Indium Metal

Abstract

The electric quadrupole hyperfine interaction at indium surfaces has been detected with use of the perturbed angular correlation technique. The electric-field gradient at the surface is found to be $\left|V_{\mathrm{zz}}\right(\mathrm{surface}\left)\right|=5.6\left(6\mathrm{}\right)\mathrm{}\times {10}^{17}$ V/${\mathrm{cm}}^2$ with an orientation perpendicular to the surface. This is a drastic enhancement of the field gradient compared with bulk by a factor $\left|\frac{V_{\mathrm{zz}}\left(\mathrm{surface}\right)}{V_{\mathrm{zz}}\left(\mathrm{b}\mathrm{u}\mathrm{l}\mathrm{k}\right)}\right|\approx 4$. The result is discussed in a simple one-Wigner-Seitz-cell model.