ABSOLUTE (E,2E) COPLANAR SYMMETRIC CROSS-SECTIONS MEASURED FOR VALENCE ORBITALS OF NE

Absolute (e,2e) five times differential cross sections, measured in coplanar symmetric conditions, for the outermost 2s and 2p orbitals of neon are reported. The incident energy is varied from 200 to 3600 eV in order to test different theoretical models. The averaged eikonal distorted-wave impulse approximation is a reasonable approximation at incident energies larger than 200 eV and recoil momenta less than 1 au, provided the effective two-body operator is the t matrix and not the nu matrix. The imaginary part of the averaged eikonal potential is non-zero only for the 2s orbital. Previous indications that the impulse approximation breaks down for small relative momenta between the outgoing electrons are confirmed by these measurements.