An optical absorption (OA) band of interstitial dichlorine monoxide molecules with peak at 4.7 eV and halfwidth 0.94 is identified in F2 laser - irradiated (photon energy=7.9 eV) synthetic silica glass bearing both O2 Cl2 molecules. Alongside intrinsic defects, this OA can contribute to solarization glasses produced from SiCl4. While the formation ClClO confirmed by its Raman signature, structu...