Comparison of local exchange potentials for electron-N₂ scattering

We consider vibrationally and electronically elastic electron scattering by N₂ at 2-30 eV impact energy. We consider static, static-exchange, and static-exchange-plus-polarization potentials, Cade-Sales-Wahl and INDO/1s wave functions, and semiclassical exchange and Hara free-electron-gas exchange potentials. We show that the semiclassical exchange approximation is too attractive at low energy for N₂. We show quantitatively by consideration of partial and total integral cross sections how the effects of approximations to exchange become smaller as the incident energy is increased until these differences are about 8% for the total integral cross section at 30 eV.