Magnetic resonance studies on radiation-induced point defects in mixed oxide glasses. I. Spin centers in B2O3 and alkali borate glasses

Radiation-induced spin centers in vitreous boron trioxide and alkali berate glasses were studied using pulsed electron paramagnetic resonance (EPR). I t is shown that electrons and holes in these glasses are trapped on valence alternation defects, undercoordinated oxygen (holes) and overcoordinated o xygen (electrons). The local environment around these defects has major eff ect on spin parameters of the corresponding spin centers. The electronic an d atomic structure of spin-1/2 centers and their diamagnetic precursors is analyzed using semiempirical and ab initio calculations. (C) 2000 Elsevier Science B.V. All rights reserved.