Properties of electron-irradiation-produced O2-in Ca(OH)2

Abstract

O2- centres can be produced in Ca(OH)2 by irradiation with 1.5 MeV electrons. The centres have been identified and their properties were studied by means of ESR, ENDOR, optical absorption and Raman measurements. A simple apparatus for the growth of large single crystals of Ca(OH)2 is described. The results of the measurements of the g tensor can be understood in terms of a model developed for O2- in alkali halides. The authors have also measured the hyperfine interaction with the 17O nuclear spin in a 17O enriched powder and in a single crystal. The results fit the model. The optical spectra show the characteristic O2- absorption at 4.92 eV. From the Raman spectra the vibrational constants were calculated. It was determined from the ENDOR spectra that the O2- centre is located at an OH- site. The interaction of the centre with the neighbouring proton spins can be described in terms of a Hamiltonian with a purely dipolar interaction term and an isotropic hyperfine term. Almost no covalency is expected.