Electron Momentum Distributions of the Highest Occupied Molecular Orbital of CF3Br： Delocalization of Halogen Lone-Pair Orbitals

The highest occupied molecular orbital (HOMO) of trifluorobromomethane (CF3Br) is studied by binary (e,2e)electron momentum spectroscopy. The experimental momentum profile of the HOMO is compared with the Hartree-Fock (HF) and density functional theory (DFT-B3LYP) calculations. The calculated results largely depend on the size of basis sets rather than theoretical methods. Both the HF and DFT calculations using the 6-311 G^** basis set give a good explanation to the experiment. Delocalization of halogen lone-pair orbitals in the series molecules CF3X (X=F, Cl, Br) has been investigated.