Comment on luminescence of fused silica: Observation of the O2- emission band

Contrary to the recent suggestion, the photoluminescence center responsible for the well-known 3.1-eV emission band in fused silica is not due to O2- centers. It is nonparamagnetic and associated with Ge impurities. The reported vibrational structure of the 3.1-eV band is not confirmed. The low-temperature photoluminescence band at 2.7 eV and the vibrational structure are due to a contaminating film, accumulated on the surface of the sample under poor vacuum conditions.