Measurement of the rate coefficient for collisional removal of O2(X 3Σg-,υ=1) by O(3P) -: art. no. 194303

We report a laboratory measurement of the rate coefficient for the collisional removal of O-2(X(3)Sigma(g)(-),upsilon=1) by O(P-3) atoms. In the experiments, 266-nm laser light photodissociates ozone in a mixture of molecular oxygen and ozone. The photolysis step produces vibrationally excited O-2(a(1)Delta(g)) that is rapidly converted to O-2(X(3)Sigma(g)(-),upsilon=1-3) in a near-resonant electronic energy-transfer process with ground-state O-2. In parallel, a large amount of O(D-1) atoms is generated that promptly relaxes to O(P-3). Under the conditions of the experiments, only collisions with the photolytically produced O(P-3) atoms control the lifetime of O-2(X(3)Sigma(g)(-),upsilon=1), because its removal by molecular oxygen at room temperature is extremely slow. Tunable 193-nm laser light monitors the temporal evolution of the O-2(X(3)Sigma(g)(-),upsilon=1) population by detection of laser-induced fluorescence near 360 nm. The removal rate coefficient for O-2(X(3)Sigma(g)(-),upsilon=1) by O(P-3) atoms is (3.2 +/- 1.0)x10(-12) cm(3) s(-1) (2 sigma) at a temperature of 315 +/- 15 K (2 sigma). This result is essential for the analysis and correct interpretation of the 6.3-mu m H2O(nu(2)) band emission in the Earth's mesosphere and indicates that the deactivation of O-2(X (3)Sigma(g)(-),upsilon=1) by O(P-3) atoms is significantly faster than the nominal values recently used in atmospheric models.