Decay kinetics of photoluminescence (PL) existing around 2.7 eV has been studied in various ion‐implanted thermal SiO2films as a function of implantation conditions. The PL observed in many samples shows decay constants shorter than 10 ms, which is a well‐observed decay constant for silica glass. The change in the decay constant and that in the PL intensity have been found to be systematically related with the mass and the dose of the implanted ions. Therefore, despite the short decay constant, the present 2.7 eV PL is attributable to a triplet‐to‐singlet transition of oxygen deficient centers, as in the case of silica glass. The rapid decay is interpreted as the increase in spin‐orbit coupling interaction due to structural deformations by ion implantation such as the formation of paramagnetic defects and/or densification. ©1996 American Institute of Physics.