Absorption of iron and water in the Na2O-CaO-MgO-SiO2 glasses. II. Selection of intrinsic, ferric, and ferrous spectra in the visible and UV regions

Absorption spectra of a number of 13Na(2)O-10CaO-6MgO-71SiO(2) glass sample s doped with iron were studied in the spectral range 3000-200 nm (3300-50 0 00 cm(-1)). The concentration of Fe2O3 in the glasses was varied from 8 x 1 0(-4) to 0.9 wt%. The absorption spectra of glass matrix, hydroxyl groups, ferric (Fe3+) and ferrous (Fe2+) ions were determined from experimental spe ctra. The exponential intrinsic absorption edge was found in the region of 213 nm (47 000 cm(-1)) in glasses with iron oxide concentration less than 1 0(-3) wt%. Absolute specific absorption spectra of Fe3+ and Fe2+ were deter mined for the whole spectral region. The absorption bands for the ferrous i on were observed in the region of 400 nm (25 000 cm(-1)) and for ferric ion at 500 nm (20 000 cm(-1)) which, to our knowledge, has not been reported. A simple algorithm was developed to describe the absorption of glass as a s um of absorption spectra of the glass matrix, hydroxyl and both forms of ir on. (C) 1998 Elsevier Science B.V. All rights reserved.