Evaluating data for atmospheric models, an example: IO + NO2 = IONO2.
Data for the title reaction have been fit to the different formalisms used by the NASA and IUPAC data evaluation panels. The data are well represented by either formalism. Reported values for the bond dissociation energy at 0 K, D0(IO-NO2) vary from about 95 to 135 kJ mol(-1), with uncertainty ranges of about 20 kJ mol(-1). Master equation/RRKM methods were employed in an attempt to reconcile these values with the data. This was possible within reasonable bounds and suggests a value in the neighborhood of 150 kJ mol(-1). As always, there are sufficient assumptions and unknowns in such an attempt, that this value is somewhat uncertain, but the true value is not expected to be too far from this result. Thus, it is possible to evaluate data of the type addressed here in a manner reasonably consistent with the basic understanding of pressure dependent rate coefficients for use in atmospheric or other models of "engineering" problems. There are, however, strict limits on our ability to know specific details. It is possible that true anharmonicity corrections that include stretch-bend interactions as well as effects due to averaging rotational contributions could combine to lower this value by as much as 10 kJ mol(-1). In addition collision and energy transfer parameters are somewhat uncertain.
Golden
David M
DM
Department of Mechanical Engineering, Stanford University, Stanford, California 94305, USA. david.golden@stanford.edu