Electron spin resonance studies of the Ag2+ ion produced in Ag-X zeolite by γ irradiation

The silver-X zeolite was prepared and γ-irradiated by 60Co at room temperature. ESR measurements were made at -1960C. A figure shows the ESR spectrum observed for silver-X γ-irradiated after evacuation at 3500C. The anisotropic g factors, and the anisotropic hyperfine splittings obtained agree well with those of the divalent silver ion. The Ag2+ spectrum was broadened by exposing the sample to 150 Torr of oxygen, suggesting that the Ag2+ ions are located at the sites in the supercage. Upon the introduction of water vapor, the Ag2+ disappeared, suggesting that the polarization of water may result in the transfer of negative charge from anion center irradiation, and reduce the ion to Ag+. The effect of pretreatment temperature on the intensity of the Ag2+ spectrum increases up to 3500, then it gradually decreases as the temperature increases, indicating that the zeolite structure can no longer stabilize the Ag2+ ion. The exposure of γ-irradiated Ag-X to pyridine changed the ESR spectrum showing 8 superhyperfine lines due to nitrogen nuclei, indicating 2 or 3 pyridine molecules adsorbed on one silver ion. The ESR spectrum of Ag2+ disappeared upon heating the γ-irradiated sample to 1500C, while the spectrum with nitrogen superhyperfine lines disappeared at 1000C