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.

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Published in Physical Review A, v. 97, issue 5, 052710, p. 1-7.

©2018 American Physical Society

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This work was supported by the United States National Science Foundation under Grants No. PHY-0855040 and No. PHY-1607140 (N.L.S.M.), No. PHY-1402899 and No. PHY-1708108 (B.A.dH.), No. PHY-1403245 (K.B.), and No. PHY-1520970 (O.Z. and K.B.).