Electron paramagnetic resonance and optical absorption studies of Cu2+ ions in alkali barium borate glasses

Electron Paramagnetic Resonance (EPR) and optical absorption studies have been made for Cu2+ ions in alkali barium borate glasses. The EPR spectrum consists of four hyperfine lines characteristic of Cu2+ ions. From the observed spectra the spin-Hamiltonian parameters have been evaluated. The values of spin-Hamiltonian parameters indicate that the Cu2+ ions in alkali barium borate glasses were present in octahedral coordination with a strong tetragonal distortion. The linewidth of the parallel and perpendicular hyperfine peaks increases in order with magnetic quantum number of copper nuclei and this has been attributed to the microenvironmental fluctuations around Cu2+ ion which is intrinsic to the glassy state. The optical absorption spectra of Cu2+ ions doped glasses show a single broad absorption band which is attributed to B-2(1g)-->B-2(2g) transition. By correlating the EPR and optical data, the molecular orbital coefficients have been evaluated. The theoretical values of optical basicity (Lambda(th)) of these glasses have also been evaluated. (C) 1998 Elsevier Science S.A.