Giant enhancement of network coherence through mixed alkali oxide addition to rapidly quenched vitreous silica.

I explain theoretically the dramatic 5-fold enhancement of the scattering strength of one of the "bulk" or "intrinsic" Raman bands of vitreous silica recently observed by Kamitsos and Risen. This enhancement is achieved only through the combined effect of two factors, mixed alkali addition and rapid quenching. Relative to single alkali addition, scattering from all other vibrational bands, including the "defect" bands, is almost unchanged. A theoretical model which explains this highly selective behavior is proposed.