Electron-Nuclear Double Resonance of Ag Nuclei in AgC1+Fe3+

The electron nuclear double resonance (ENDOR) spectra of both isotopes ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$ and ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$ have been measured at 1.3 °K in a single crystal of silver chloride containing 0.0006% ${\mathrm{Fe}}^{3+}$ ions. The angular variation of the ENDOR spectrum agrees with that calculated from the tetrahedral model proposed by Hayes, Pilbrow, and Slifkin in which the iron ion occupies the interstitial site, the four nearest-neighbor silver ions being absent. The superhyperfine structure (super-hfs) constants of the second, third, and fourth neighbor ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$ and ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$ nuclei with the magnetic electrons in the ferric iron were obtained together with the directions of their principal axes. The isotropic hf interactions are probably due to indirect I·S couplings between the neighboring Ag nuclei and the magnetic electrons on the ferric iron via conduction electrons in the excited states.