Ultraviolet-excited radiative decay channels of defect states in high-density sixfold-coordinated SiO2

Optical emissions at 2.1, 2.6, 3.0, and 4.5 eV, excited by synchrotron radiation from 5 to 18 eV, were found in stishovite, a high-density sixfold-coordinated SiO2 polymorph. Luminescence and lifetime data were analyzed from 10 to 300 K showing a transition scheme distinct from that of silica, despite some similarities in the spectral positions. The results give a basis for the study of defect structures in sixfold-coordinated SiO2 environments, for theoretical calculations of the optical response of high-density SiO2, and for a microfluorescence identification of geologic stishovite.