Ab initio study on the potential energy hypersurface of FC(O)O+

The equilibrium structure, vibrational spectra, and adiabatic ionization potential for FC(O)O+ have been investigated using high-levels of ab initio theory. Methods included second-order Møller-Plesset perturbation theory (MP2), the singles and doubles configuration interaction (CISD) method, quadratic configuration interaction method including single and double excitations (QCISD), and singles and doubles coupled-cluster theory which incorporates a perturbational estimate of the effects of connected triples excitation [CCSD(T)]. The CCSD(T) method is found to yield quite accurate results for FCO+, which is used as a calibrant for FC(O)O+. At the highest level of theory, CCSD(T)/6–311 + G(3df)//CCSD(T)/6–311G(2df), the adiabatic ionization potential for FC(O)O+ is predicted to be 287.4 kcal mol−1 (12.5 eV).