Far-uv photolysis of O2 produces excited atoms O(1D) whose relative quenching constants with argon, krypton, and neon are k Ar = 0.015, kKr= 0.09, kNe = 0.007 if k xe is taken as unity. These values are in good agreement with Cvetanovic's relative efficiencies [J. Chem. Phys. 45, 8, 2888 (1966)].