Correlation between the radiation-induced intrinsic 4.8 eV optical absorption and 1.9 eV photoluminescence bands in glassy SiO2

Abstract

The controversial relationship between the intrinsic 1.9 eV photoluminescence (the R band), the 2.0 and 4.8 eV excitation/optical absorption bands is examined for 11 specimens with different OH, Cl, and O2 concentrations and with different irradiation histories. The direct relation is found between the intensities of the R-band luminescence measured with the 4.0 eV (IUV) or resonance (1.94 eV) excitation (Ires), although it is slightly superlinear, Ires∝(IUV). The deviation from the exactly constant ratio between the band intensities in different glass samples is attributed mainly to the inhomogeneous broadening effects. Also, nonzero polarization degree, P=−1.5±0.5%, in the R-band maximum region is reconfirmed upon linearly polarized 4.8 eV excitation, substantiating a close relation between the 4.8 eV absorption band and the R band. These results suggest strongly that both of the two absorption bands at 2.0 and 4.8 eV are originated from a single center, and quantitatively agree with the recently proposed optical transition scheme in the nonbridging oxygen hole center.