Time-differential perturbed angular correlation of 140Ce implanted in highly oriented pyrolytic graphite

Using an ion implantation method, we introduced cerium nuclei in highly oriented pyrolytic graphite (HOPG), and have studied their behavior by means of the time-differential perturbed angular correlation technique. The time-variant directional anisotropy for the present pseudo-single crystalline sample is little different from that for poly-crystalline graphite. Temperature dependence has been observed on the electric quadrupole interaction between the probe nuclei and the extranuclear charge distribution; the anisotropy shows gradual attenuation at room temperature, whereas the effect of an electrostatic perturbation is implied in the spectrum at 10 K. For the chemical state of the probe atom in HOPG, the trivalent state is suggested from the large magnitude of the electric field gradient at the probe nucleus. (author)