title: Collisional relaxation of O2(X3Σg(-), υ = 1) and O2(a1Δg, υ = 1) by atmospherically relevant species.
abstract: Laboratory measurements are reported of the rate coefficient for collisional removal of O(2)(X(3)Σ(g)(-), υ = 1) by O((3)P), and the rate coefficients for removal of O(2)(a(1)Δ(g), υ = 1) by O(2), CO(2), and O((3)P). 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)Δ(g), υ = 1), and the output of the second laser detects O(2)(a(1)Δ(g), υ = 1) via resonance-enhanced multiphoton ionization. The kinetics of O(2)(X(3)Σ(g)(-), υ = 1) + O((3)P) relaxation is inferred from the temporal evolution of O(2)(a(1)Δ(g), υ = 1), an approach enabled by the rapid collision-induced equilibration of the O(2)(X(3)Σ(g)(-), υ = 1) and O(2)(a(1)Δ(g), υ = 1) populations in the system. The measured O(2)(X(3)Σ(g)(-), υ = 1) + O((3)P) 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)Δ(g), υ = 1) by O((3)P), 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)Δ(g), υ = 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)Δ(g), υ = 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.
authors.affiliation: Molecular Physics Laboratory, SRI International, 333 Ravenswood Ave., Menlo Park, California 94025, USA. dusan.pejakovic@sri.com
authors.forename: Dušan A
authors.initials: DA
authors.lastname: Pejaković
authors.forename: Zachary
authors.initials: Z
authors.lastname: Campbell
authors.forename: Konstantinos S
authors.initials: KS
authors.lastname: Kalogerakis
authors.forename: Richard A
authors.initials: RA
authors.lastname: Copeland
authors.forename: Tom G
authors.initials: TG
authors.lastname: Slanger