Photoelectron spectra of fluorotribromomethane and fluorotrichloromethane

High resolution He(I) photoelectron spectra are reported for fluorotribromomethane CFBr₃ and fluorotrichloromethane CFCl₃. The assignments are based on CNDO/2 calculations, symmetry arguments, the fine structures of the bands, and comparison with the photoelectron spectra of related compounds. Linear relationships have been found between the Pauling electronegativity values for the halogen atoms and the observed vertical ionization energies corresponding to a₂ of a₂′ orbitals of CFX₃ and related compounds CHX₃, OPX₃, BX₃ and PX₃ (X = F, Cl, Br, I).