Electron paramagnetic resonance study of hydrogen atoms trapped in γ-irradiated Y type zeolites exchanged with different cations

Abstract

H atoms trapped after the γ-irradiation at 77 K of Y type zeolites exchanged with different cations have been studied using e.p.r. spectroscopy. The H atom yield is dependent on the acidic structural OH group content and it is postulated that the mechanism of formation and trapping of H atoms follows the following equilibrium: [graphic omitted] The H atom yield is related to the acidity and mobility of the hydrogen of the hydrogen of the hydroxyl groups and to the trapping strength. The trapping strength of H atoms, characterized by the values of both the hyperfine coupling constant with respect to the free H atom, and the activation energy of recombination, is strongly dependent on the nature of the exchanged cation, and follows the sequence K > Na [double greater-than, compressed] Ca > La.