This compilation contains critically evaluated kinetic data on elementary homogeneous gas phase for use in modelling processes. Data sheets are presented for some 196 Each data sheet sets out relevant data, rate coefficient measurements, an assessment of the reliability of the data, references, and recommended rate parameters. Tables summarizing the preferred rate data are also given. The considered are limited largely to those involved in the of and ethane in air but a few relevant to the chemistry of exhaust gases and to the of aromatic compounds are also included.

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Abstract. This article, the first in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of O x , HO x , NO x and SO x species, which were last published in 1997, and were updated on the IUPAC website in late 2001. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and five appendices containing the data sheets, which provide information upon which the recommendations are made.

This paper describes the calculation of rate constants for thermal unimolecular reactions and recombinations at the low pressure limit, at the high pressure limit, and in the intermediate falloff range, as well as the calculation of specific rate constants for unimolecular rearrangements. The most uncertain factors of the theory are identified by comparison with the N02, CIÑO, H20, and 03 systems. Weak collision and centrifugal barrier effects are discussed for low pressure rate constants. Simplified adiabatic channel calculations are proposed for specific rate constants and high pressure rate constants. Reduced falloff curves are presented in factorized form with weak collision and strong collision broadening factors. Simple falloff expressions are derived.

The master equation for a thermal unimolecular reaction in gases at low pressures is formulated. Steady-state solutions are derived in analytical form with an exponential model of collisional transition probabilities, (i) for vibrational energy transfer in molecules with variable densities of states, and (ii) for combined rotational and vibrational energy transfer in molecules with variable heights of the centrifugal barriers. Other models of transition probabilities are treated numerically. The diffusion limit of energy transfer is discussed. In all cases, the nonequilibrium populations of excited states and the weak collision efficiency factors βc are calculated.