Theoretical studies of the photoelectron spectroscopy of the fluorinated ethylenes

A b initio molecular orbital calculations within the self-consistent field (SCF) method were effected for the complete series of the fluorinated ethylenes. A ‘‘double zeta’’-quality basis set was used with complete geometry optimization. Two methods were employed to correlate these calculated results with experimentally obtained vertical ionization potentials: the use of the orbital energies in accordance with Koopmans’ theorem and the use of the difference between the SCF energy of the molecule and the respective ion constrained to the molecular geometry. In several cases, an average of the Koopmans’ theorem results and the ΔSCF results was employed to approximate the experimental photodetachment energies. Definitive assignments of the molecular orbitals to the experimental bands could not be made on the basis of correspondence of energies. However, the relative ordering of the theoretical energies is considered generally correct. A correspondence also exists between the experimentally determined characteristics of the molecular orbitals, where specified, and the theoretical characteristics as evidenced in the population analyses. The orbital assignments were based upon the latter two factors.