Spectrochemical studies on charge transfer bands due to d0, d5 and d10 ions in a sodium silicate glass

Abstract

Titanium, vanadium and copper are normally present in glasses in their variable valency states but only Ti⁴⁺ (3d⁰), V⁵⁺ (3d⁰) and Cu⁺ (3d¹⁰) ions were found to exhibit charge transfer bands in glasses in the ultra-violet region of light. The molar extinction coefficients of these ions were calculated at their wavelength maxima in a 30Na₂O·70SiO₂ glass using Beer's-Bouger's equation and the intensities of their bands were found to lie of the order of around 10³ gm mol lit⁻¹cm⁻¹. The values of the molar extinction coefficients for these ions were compared with those of Ce⁴⁺ (5d⁰), Cr⁶⁺ (3d⁰) and Fe³⁺ (3d⁵) ions calculated earlier in 30Na₂O·70SiO₂ glass at their wavelength maxima in UV-region. The mechanism of electronic transition was suggested as L → M, M → L and M → L → M charge transfer available till date as a result of absorption of high energy UV-radiation extensively for d⁰, d⁵ and d¹⁰ ions respectively in glass depending upon the glass melting conditions. The low energy tail, of the UV-bands due to all these ions were found to obey Urbach's Rule in the present sodium silicate glass. The intensities of the charge transfer bands due to these ions are expected to depend upon their nature and symmetries, electronic configurations and wavelength of maximum absorption in the glass.