[en] Superexcited molecules are unusual species that at present can only be investigated using nuclear recoil methods. The thermochemical technique for measuring the excitation energy distributions of superexcited molecules is reviewed and applied to recent studies of CF₃¹⁸F and C₂F₅¹⁸F formed from high energy atomic exchange reactions in CF₄ and C₂F₆. The nascent CF₃¹⁸F and C₂F₅¹⁸F range in energy from 1.7 to about 45 eV. The average energies of these products range from 15 to 20 eV. The internal excitation that accompanies these reactions is initially localized near the ¹⁸F bonding site, and the C₂F₅¹⁸F decomposition mechanism is non-statistical. Moderated nuclear recoil experiments yield mechanisms and rates for the reactions of thermal ¹⁸F atoms. Under our standard experimental conditions from 3.4 x 10⁴ to 3.4 x 10⁸ labeled product molecules are available for radioassay. This procedure is free from systematic error and the measurements yield exceptional precision and sensitivity because (1) high energy reactions with the thermally active reagents are suppressed. (2) the host environment is rigorously controlled, and (3) the molecular products from many single atom reactions are directly counted. The limitations of this technique are described and results are presented for the reactions of thermal ¹⁸F atoms with CH₄ and C₂H₄. (J.P.N.)