Optical Absorption of Excimer Laser-Induced Dichlorine Monoxide in Silica Glass and Excitation of Singlet Oxygen Luminescence by Energy Transfer from Chlorine Molecules

An optical absorption (OA) band of interstitial dichlorine monoxide molecules with peak at 4.7 eV and halfwidth 0.94 eV is identified in F₂ laser-irradiated (ħω = 7.9 eV) synthetic silica glass bearing both interstitial O₂ and Cl₂ molecules. Alongside with intrinsic defects, this OA band can contribute to solarization of silica glasses produced from SiCl₄. Although only the formation of ClClO is confirmed by its Raman signature, its structural isomer ClOCl may also contribute to this induced OA band. Thermal destruction of this band between 300 °C and 400 °C almost completely restores the preirradiation concentration of interstitial Cl₂. An additional weak OA band at 3.5 eV is tentatively assigned to ClO₂ molecules. The strongly forbidden 1272 nm infrared luminescence band of excited singlet O₂ molecules is observed at 3–3.5 eV excitation, demonstrating an energy transfer process from photoexcited triplet Cl₂ to O₂. The energy transfer most likely occurs between Cl₂ and O₂ interstitial molecules located in neighboring nanosized interstitial voids in the structure of SiO₂ glass network.