Reaction in mixtures of D2–F2–O2–CO2 dilute in Ar has been initiated by pulsed irradiation with a XeCl laser, and the resulting time-dependent infrared emission from the ν3 vibrational band of CO2 has been monitored. Experimental conditions were chosen such that the rate of DF formation and the decay of the emission were controlled by the rate of the reaction D + O2+ M → DO2+ M. Rate constants (10–32 cm6 s–1) at room temperature, determined from the measured emission decay, for M = Ar, CO2, D2 and F2 are 1.7 ± 0.1, 15.9 ± 1.0, 7.1 ± 0.5 and 31.1 ± 3.9, respectively.