Chemical CO and CO2 lasers produced from the CH + O2 reaction

Abstract

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 Δν = 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, N2, N2O, and CO2) were investigated. The stimulated emission is concluded to result primarily from the four-centered reaction CH+O2→ lim 1CO†+OH†,Δ H10=−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→ lim 10H+CO2†,Δ H100=−184 kcal/mole. This is the first example of lasing from a chemically produced excited polyatomic molecule. When a small amount of N2O or CO2 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.