Strong 5 μm CO laser emission was observed in the flash photolysis (λ ≥ 165 nm) of mixtures of O2 and CHBr3 in the presence of large amounts of diluent (SF6, Ar, or He). About 60 vibration-rotation transitions were identified in the range between Δv = 14→13 and 2→1. The laser intensity was found to vary linearly with flash energy. The effects of various additives (He, Ar, SF6,CO N 2, N2O, and CO2) were investigated. The stimulated emission is concluded to result primarily from the four-centered reaction CH+O2→1 CO†+OH†, ΔH 10=-159 kcal/mole. Other possible minor reactions were also considered. No OH emission was detected under the same experimental conditions. With the aid of a band-pass filter (8.6-15 μm range), 10 μm CO2 emission was observed concurrently with the 5 μm CO emission. The CO2 emission, which consisted of the P(58)-(70) lines of the (001)→(020) band, was found to vary strongly with the partial pressure of O2. Since both the intensity of this emission and the yield of CO2 increased linearly with flash energy, the (001)→(020) CO2 emission is believed to be the direct consequence of the following CH+O2 reaction: CH+O2→ 10H+CO2†, ΔH100 = -184 kcal/mole. This is the first example of lasing from a chemically produced excited polyatomic molecule. When a small amount of N2O or CO 2 was added to the O2-CHBr3-He mixture, the regular (001)→(100) band of both molecules began to lase at ∼P(18)-P(28), presumably resulting from the energy transfer process OH† + M(000)→OH+M(001), where M=CO2 or N2O.