A flow system was set up to measure the quenching probability ~ of O2（1△g） on various O2- adsorbed metal surfaces including Cu, Cr, Ni, and Ag. increased with both the duration of the experiment and the O2（1△g） concentration. After several hours evacuation to a few Pa, γ can return to its original value. A deactivation mechanism of O2（1△g） is suggested by considering first the weak chemisorption of O2（1△g） on the surface adsorption sites, followed by the near resonant energy transfer between the gas phase O2（1△g） and surface O2（1△g）. A phenomenological model in accord with the experimental fact has been proposed together with relevant kinetic equations.
