The Reaction Cl + NO2 → ClONO and ClNO2

Measurement of the Intramolecular Hydrogen-Shift Rate Coefficient for the CH3SCH2OO Radical between 314 and 433 K

The intramolecular hydrogen-shift rate coefficient of the CH₃SCH₂O₂ (methylthiomethylperoxy, MSP) radical, a product formed in the oxidation of dimethyl sulfide (DMS), was measured using a pulsed laser photolysis flow tube reactor coupled to a high-resolution time-of-flight chemical ionization mass spectrometer that measured the formation of the DMS degradation end product HOOCH₂SCHO (hydroperoxymethyl thioformate). Measurements performed over the temperature range of 314-433 K yielded a hydrogen-shift rate coefficient of k₁(T) = (2.39 ± 0.7) × 10⁹ exp(-(7278 ± 99)/T) s^-1 Arrhenius expression and a value extrapolated to 298 K of 0.06 s^-1. The potential energy surface and the rate coefficient have also been theoretically investigated using density functional theory at the M06-2X/aug-cc-pVTZ level combined with approximate CCSD(T)/CBS energies yielding k₁(273-433 K) = 2.4 × 10¹¹ × exp(-8782/T) s^-1 and k₁(298 K) = 0.037 s^-1 in fair agreement with the experimental results. Present results are compared with the previously reported values of k₁(293-298 K).

Pressure dependent reactions for atmospheric and combustion models

In order to characterize reactions as functions of temperature, pressure (molecular density) and the nature of the species that constitute that molecular density, master equation solutions are required. In this tutorial review, the application of the Multiwell suite of codes to some reactions of interest in atmospheric and combustion chemistry is discussed, with attention given to the details of the molecular and energy transfer values. Uncertainties in data and in structural and energetic molecular parameters combine to assure the need for optimization and collaborative processing of the entire data base when modeling practical systems.