Distorted Wave Effects of the 1b_3g Orbital in Ethylene

We study the unexpected distorted wave effects of the 1b_3g orbital in ethylene using a high resolution binary (e, 2e) electron momentum spectrometer, at an impact energy of 800eV plus the binding energy (8-22eV) with symmetric non-coplanar kinematics. The experimental momentum profile of the 1b_3g orbital is obtained and compared with the data previously measured at impact energy of 1200 eV plus the binding energy. Also, the experimental momentum profiles of the 1b_3g orbital are compared with the theoretical momentum distributions calculated by using Hartree-Fock and density functional theory methods. The experimental momentum profiles of the 1b_3g orbital of ethylene at different impact energies show that the cross section of the orbital below the momentum p～1 a.u. is higher for lower impact energy.