Accurate Calculations of the Electron Affinity and Ionization Potential of the Methyl Radical

The electron affinity and ionization potential for the CH 3 radical have been calculated at high levels of ab initio molecular orbital theory. The best values are obtained by extrapolating CCSD(T)/aug-cc-pVxZ values where x = D, T, Q to the complete basis set limit. Zero-point energies were calculated at the CCSD(T)/aug-cc-pVTZ level and scaled to appropriate experimental values. The calculated values are EA(CH 3 ) = 1.64 ± 0.3 kcal/mol as compared to the experimental value of 1.84 ± 0.69 kcal/mol and IP(CH 3 ) = 9.837 ± 0.01 eV as compared to the experimental value of 9.843 ± 0.001 eV. The theoretical values included estimates of relativistic and core/valence correlation effects.