Temperature and pressure dependence of the addition reactions of HO to NO and to NO₂. IV. Saturated laser-induced fluorescence measurements up to 1400 bar

The recombination reactions HO+NO+M⇒HONO+M(1) and HO+NO₂+M⇒HNO₃+M(2) have been investigated over an extended pressure (1-1000 bar) and temperature (250-400 K) range. HO radicals were generated by laser flash photolysis of suitable precursors and their decays were monitored by saturated laser-induced fluorescence (SLIF) under pseudo-first-order conditions. The measured rate constants were analyzed by constructing falloff curves which provide the high pressure limiting rate constants k_∞. In the given temperature range, these rate constants are k_1,∞ = (3.3±0.5)×10^-11×(T/300 K)^-(03±03) and k_2,∞ = (7.5±2.2) × 10^-11 cm³ molecule^-1 s^-1.