Quantitative UV–VIS spectroscopic studies of photo-thermo-refractive glasses. II. Manifestations of Ce3 + and Ce(IV) valence states in the UV absorption spectrum of cerium-doped photo-thermo-refractive matrix glasses

Abstract

The UV absorption spectra of cerium-doped photo-thermo-refractive matrix glasses were recorded and processed with the dispersion analysis based on Convolution model for the complex dielectric function. It was confirmed that the absorption maxima in the UV spectra of PTR matrix glasses related to the Ce3+ and Ce(IV) valence states are the envelopes of at least three spectral components each. The inherent frequencies of three Ce3+- and three Ce(IV)-related oscillators are shown to be located in the 31,200–34,900 and 38,400–49,800cm−1 wavenumber regions, respectively. The occurrence of three Ce3+-related spectral components was interpreted, based on an analogy with the spectra of cerium-doped crystals, in terms of splitting the excited 2D state by the non-central Coulomb and spin–orbit interactions into three levels. Beer Law was shown to be obeyed, for both the Ce3+ and Ce(IV) species, throughout the entire range of CeO2 content of samples studied. The total molar absorptivity of the strongest Ce(IV)-related oscillator was found to exceed that of the strongest Ce3+-related one by approx. 16 times. The trivalent antimony was shown to play the role of a reducer with respect to the Ce(IV) valence state.