Experimental evidence of the existence of 2 variants of the Eγt centers induced into silica by γ-rays at room temperature was reported. The 2 variants were distinguishable by the fine features of their line shapes in paramagnetic resonance spectra. These features suggested that the two Eγt differed in their topology. a thermally induced interconversion between the centers was found, with an activation energy of about 0.034eV. Signs were also found of the existence of a structural configuration of minimum energy and of a metastable state.

Structural Relaxation of Eγt Centers in Amorphous Silica. S.Agnello, R.Boscaino, G.Buscarino, M.Cannas, F.M.Gelardi: Physical Review B, 2002, 66[11], 113201 (4pp)