Spectroscopic parameters related to non bridging oxygen hole centers in amorphous-SiO2

TL;DR

This study investigates the spectroscopic parameters of non-bridging oxygen hole centers in amorphous silica, revealing linear correlations between luminescence and absorption bands, and providing insights into optical transition efficiencies and excitation pathways.

Contribution

It offers new quantitative spectroscopic parameters and confirms the defect model linking luminescence and absorption in silica.

Findings

Linear correlation between luminescence and absorption bands.

Oscillator strength of 4.8 eV transition is ~200 times higher than 2.0 eV.

Luminescence quantum yield varies with excitation energy.

Abstract

The relationship between the luminescence at 1.9 eV and the absorption bands at 2.0 eV and at 4.8 eV were investigated in a wide variety of synthetic silica samples exposed to different gamma- and beta-ray irradiation doses. We found that the intensities of these optical bands are linearly correlated in agreement with the model in which they are assigned to a single defect. This finding allows to determine spectroscopic parameters related to optical transitions efficiency: the oscillator strength of the 4.8 eV results ~200 times higher than that of the 2.0 eV; the 1.9 eV luminescence quantum yield under 4.8 eV excitation is lower (by a factor ~3) than that under 2.0 eV excitation. These results are consistent with the energetic level scheme, proposed in literature for non bridging oxygen hole center, and account for the excitation/luminescence pathways occurring after UV and visible absorption