Collisional relaxation of O_2(X_3Σ _g~-, 1) and O_2(a~1_g, ν = 1) by atmospherically relevant species

摘要

Laboratory measurements are reported of the rate coefficient for collisional removal of O_2(X_3g-, 1) by O(~3P), and the rate coefficients for removal of O_2(a~1_g, 1) by O_2, CO_2, and O(~3P). A two-laser method is employed, in which the pulsed output of the first laser at 285 nm photolyzes ozone to produce oxygen atoms and O_2(a ~1_g, 1), and the output of the second laser detects O _2(a~1_g, 1) via resonance-enhanced multiphoton ionization. The kinetics of O_2(X3g-, 1) O(~3P) relaxation is inferred from the temporal evolution of O_2(a~1_g, 1), an approach enabled by the rapid collision-induced equilibration of the O_2(X3g-, 1) and O_2(a~1_g, 1) populations in the system. The measured O_2(X ~3g-, 1) O(~3P) rate coefficient is (2.9 0.6) 10 ~(-12) cm~3 s~(-1) at 295 K and (3.4 0.6) 10 ~(-12) cm~3 s~(-1) at 240 K. These values are consistent with the previously reported result of (3.2 1.0) 10~(-12) cm~3 s~(-1), which was obtained at 315 K using a different experimental approach K. S. Kalogerakis, R. A. Copeland, and T. G. Slanger, J. Chem. Phys. 123, 194303 (2005). For removal of O_2(a~1_g, 1) by O(~3P), the upper limits for the rate coefficient are 4 10~(-13) cm~3 s~(-1) at 295 K and 6 10 ~(-13) cm~3 s~(-1) at 240 K. The rate coefficient for removal of O_2(a~1_g, 1) by O_2 is (5.6 0.6) 10~(-11) cm~3 s~(-1) at 295 K and (5.9 0.5) 10~(-11) cm~3 s~(-1) at 240 K. The O _2(a~1_g, 1) CO_2 rate coefficient is (1.5 0.2) 10~(-14) cm~3 s~(-1) at 295 K and (1.2 0.1) 10~(-14) cm~3 s~(-1) at 240 K. The implications of the measured rate coefficients for modeling of atmospheric emissions are discussed.