Two-electron interference in the helium (e, 2e) differential cross sectionat 64.6 eV

The unexpected sharp dip which is known to exist in the helium (e, 2e) diff erential cross section at an incident electron energy of 64.6 eV, and for e qual energies and angles of the two outgoing electrons, is known to be sens itive to three of the four available experimental parameters. We have now i nvestigated the sensitivity of the dip to the fourth parameter, the asymmet ry of the angles of the outgoing electrons, and have found that the dip exi sts over a wide range of asymmetric angles, but with an almost constant ang le between the two electrons. A two-electron interference model is proposed to explain these results.