Theoretical analysis of the binding of a positron and pair-annihilation in fluorinated benzene molecules

The binding of a positron to fluorobenzene molecules was theoretically demonstrated at Hartree-Fock level of multi-component molecular orbital theory. We confirmed that (i) 1,2-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,3,4-tetrafluorobenzene molecules have bound states for a positron, and (ii) their positron affinity (PA) and two photon pair-annihilation rate (Γ₂) are strongly correlated with their dipole moment. Analyzing the Γ₂ values for each electronic molecular orbital in all the fluorobenzene molecules, we found that the electronic valence orbitals, consisting of 2p atomic orbitals of fluorine atoms, have the dominant contribution to the total Γ₂ value.