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Zeitschrift fur Naturforschung - Section A Journal of Physical Sciences, vol.53, no.12, pp.951-954, 1998 (SCI-Expanded)
Activated and non-activated states of the zeolites NH4NaY and NH4CaA, and their NH+4 forms were prepared with an (NH4)2SO4 solution and were investigated by EPR after γ-irradiation. The formed radicals were attributed to O-2 supposed to be trapped near a trigonally coordinated framework of 27A1 (I = 5/2). Anisotropic O-2 spectra were observed, consisting of hyperfine structure due to the 27A1 framework, even at room temperature. This was attributed to the scarceness of NH+4 sites or trap sites because of the preparation of the NH+4 forms of the zeolites with an (NH4)2SO4 solution. The crystal field splittings were found and interpreted.