Out-of-Plane (\u3cem\u3ee\u3c/em\u3e,2\u3cem\u3ee\u3c/em\u3e) Measurements and Calculations on He Autoionizing Levels as a Function of Incident-Electron Energy

Out-of-scattering-plane (e,2e) measurements and calculations are reported for the three singlet helium 2ℓ2ℓ′ autoionizing levels, with 80, 100, 120, 150, and 488 eV incident-electron energies, and scattering angles 60∘, 50.8∘, 45∘, 39.2∘, and 20.5∘, respectively. The kinematics are the same in all cases: the momentum transfer is K = 2.1 a.u., and ejected electrons are detected in a plane that contains the momentum-transfer direction and is perpendicular to the scattering plane. The results are presented as (e,2e) angular distributions energy integrated over each level. They are compared with fully nonperturbative B-spline R-matrix and hybrid second-order distorted-wave + R-matrix calculations