Experimental Study of the Removal of Ground- and Excited-State Phosphorus Atoms by Atmospherically Relevant Species.

ABSTRACT

The reaction kinetics of the ground and first two excited states of atomic phosphorus, P, with atmospherically relevant species were studied at temperatures ranging from ∼200 to 750 K using a pulsed laser photolysis-laser-induced fluorescence technique. The temperature dependence of the rate coefficients is parametrized as follows (units cm3 molecule-1 s-1, 1σ errors) k(P(2P)+O2)(189 ≤ T/K ≤ 701) = (7.10 ± 1.03) × 10-12 × (T/298)1.42±0.13 × exp[(374 ± 41)/T]; k(P(2D)+O2)(188 ≤ T/K ≤ 714) = (1.20 ± 0.29) × 10-11 × (T/298)0.821±0.207 × exp[(177 ± 70)/T]; k(P(2D)+CO2)(296 ≤ T/K ≤ 748) = (5.68 ± 0.36) × 10-12 × (T/298)0.800±0.103; k(P(2D)+N2)(188 ≤ T/K ≤ 748) = (1.42 ± 0.03) × 10-12 × (T/298)1.36±0.04; k(P(4S)+O2)(187 ≤ T/K ≤ 732) = (3.08 ± 0.31) × 10-13 × (T/298)2.24±0.29. Electronic structure theory combined with RRKM calculations have been used to explain the unusual temperature dependence of P(4S) + O2. The small pre-exponential factor for the reaction results from a tight steric constraint, together with the requirement that the reaction occurs on doublet rather than sextet electronic surfaces.