Investigation of electron momentum spectroscopy for inner valence orbitals 4a_g +4b_u of diacetyl

The ionization energy spectra and the spherically averaged momentum distributions of inner valence orbitals for diacetyl have been investigated by using a high resolution (ΔE = 1.15 eV, Δp ≈ 0.1 a.u.) electron momentum spectrometer. The impact energy was 1200 eV plus binding energy (i.e. 1201-1240 eV) and a symmetric non-coplanar kinematics was employed. The experimental ionization energy spectra have been compared with the published photoelectron spectra. The momentum profiles of inner valence orbitals 4a_g + 4b_u have been compared with the theoretical calculations obtained using Hartree-Fock method and density functional theory. The measured momentum distribution is consistent with the theoretical calculations.