ELECTRON-PARAMAGNETIC-RESONANCE AND OPTICAL-ABSORPTION SPECTRA OF CU2+ IONS IN ALKALI BARIUM CHLOROPHOSPHATE GLASSES

The results of measurement of electron paramagnetic resonance and opti cal absorption spectra at room temperature of alkali barium chlorophos phate glasses (BaCl2-M2O-P2O5) doped with 1 mol% CuO are presented for various alkali compositions (M = Li, Na, K, Li-Na, Na-K and K-Li). Th e results indicate that the mixed alkalies do not produce alterations of the glass network. The ground state of Cu2+ is the d((x2-y2)) orbit al and the site symmetry that exists around the Cu2+ ions is octahedra l with a tetragonal elongation. The theoretical optical basicity of th e glasses have been evaluated and the changes in optical basicity are independent of changes in spin-Hamiltonian parameters of the Cu2+. The optical absorption spectra of Cu2+ ions for all the glass samples was single asymmetric band which corresponds to a B-2(1g) --> B-2(2g) tra nsition. By correlating the spectral data, the molecular orbital coeff icients alpha(2) and beta(1)(2) for Cu2+ have been evaluated and resul ts indicate that there is covalency for the in-plane sigma-bonding and that the in-plane pi-bonding is significantly ionic in nature. (C) 19 98 Elsevier Science B.V. All rights reserved.