Experimental and theoretical investigations on the valence orbitals of fluorobenzene by electron momentum spectroscopy

We report here an electron momentum spectroscopy study on the valence orbitals of fluorobenzene. The experiments are performed by a binary (e, 2e) spectrometer employing symmetric non-coplanar geometry at impact electron energies of 1200 and 800 eV plus binding energy. The experimental momentum distributions are compared with the theoretical calculations using Hartree-Fock and density functional theory methods within the framework of plane wave impulse approximation (PWIA). It is shown that the calculations are in generally good agreement with the measured electron momentum profiles, while the discrepancies can be mostly attributed to the distorted-wave effect. It is interesting to find that for the inner-valence orbitals, the pole strengths (PSs) obtained by comparing the experimental data with the theoretical calculations are different for different impact electron energies. This indicates that the PS can properly be determined only when the PWIA is fulfilled.