Direct observation of distorted wave effects in ethylene by a new type of (e, 2e) electron momentum spectrometer

We report here the direct measurement of electron momentum distributions for ethylene using a newly developed high performance electron momentum spectrometer at different impact energies from 400 to 2400 eV. The “turn up” effects in the (e, 2e) cross sections of the 1b3g orbital compared with the plane wave impulse approximation calculations are observed in both low and high momentum (p) regions, but such discrepancies become smaller with increase of the impact electron energies. It is suggested that the observed discrepancies are due to the distorted wave effects in molecules, which will provide experimental corroboration for theoretical calculations based on distorted waves in molecules.