High-level ab initio characterization of the multichannel Cl( 2 P 3/2 ) + C 2 H 5 I reaction

) mechanisms. Geometries and harmonic vibrational frequencies of all stationary points are determined at the MP2/aug-cc-pVDZ and CCSD(T)-F12b/aug-cc-pVDZ levels of theory, and single-point energies are further refined at the most accurate geometries using the coupled-cluster method with aug-cc-pVTZ and aug-cc-pVQZ basis sets. To target chemical accuracy, five additional energy corrections - accounting for core correlation, scalar relativistic, spin-orbit, and post-CCSD(T) effects - are incorporated into the CCSD(T)-F12b/aug-cc-pVQZ single-point energies. The resulting benchmark data allow for the detailed mapping of the reaction pathways, including the identification of transition states and pre- and post-reaction minima, which guide the system from the reactants toward the various product channels on the PES. Rate coefficients are determined using transition-state theory, including the Wigner tunneling correction, and compared to literature theoretical values.