Nuclear electric-quadrupole interaction of ion-implanted 203Hg and 69mZn in graphite

Hg203 and Zn69m ions have been implanted into thin foils of highly oriented pyrolytic graphite at room temperature and at temperatures below 1 K. Low-temperature nuclear orientation due to strong electric-quadrupole interaction has been observed and the derived electric-field gradients are compared with two kinds of theoretical calculation. The first is based on the induced polarization of the graphite atoms, while in the second the hybridization of impurity and graphite electron wave functions is calculated. The results indicate that the fraction of nuclei that contribute to the macroscopic alignment is located in the layers of the C atoms. The experimental value of Vzz at the nuclear site of Hg is +[8.2(9)]×1022 V/m2, parallel to the graphite c axis.