AN ABINITIO THEORETICAL-STUDY OF THE CH+H-2 REVERSIBLE CH3-STAR REVERSIBLE CH2+H REACTIONS

Ab initio calculations of the electronic wave function and associated potential energy of CH3 at geometries appropriate for the title reaction described here allow characterization of the reactants and the energetically most favorable routes that are followed during the reaction. The quantum mechanical description of the electronic motion at each molecular geometry involves the response of each electron to the average field of all other electrons and the approximate correlated response of each electron to the instantaneous position of the other electrons. The basic methodology for the computation of this wave function, using extensive orbital basis sets and large-scale configuration expansions, is described. This calculation is one of the largest ever attempted for the characterization of a polyatomic reaction path. However, the path description involves a fine balance of energy contributions that requires this level of sophistication. The calculated properties of the reactants, the intermediate CH3, and the reaction paths to form CH3 are presented. The computed energetics compare favorably to experimental results.