Nuclear conversion of 195AuFe into 195PtFe centers in silicon: observations by magnetic resonance

For the purposes of the reported experiments iron-doped silicon samples were implanted with nuclei 195Hg, which due to nuclear instability transmute via radioactive gold into stable platinum. Electron paramagnetic resonance was applied to monitor the conversion of 195AuFe centers into 195PtFe centers. On the basis of the hyperfine interactions both centers were unambiguously ascribed to gold and platinum impurities with mass 195, having their origin in the implantation. From the observation of centers with an equal geometrical structure, it is concluded that no atomic displacements due to recoil occur. Intensities of 195AuFe decrease with time and are accompanied by a simultaneous increase of 195PtFe signals, revealing the nuclear process. Deviation of the time dependence from the 183 days half-life of the 195Au isotope is ascribed to iron diffusion and to shift of the Fermi level in the samples during the center transformation. Accurately measured hyperfine interactions with the gold isotopes indicate a hyperfine structure anomaly of 195Au with respect to 197Au less than 1%.