Small recoil momenta double ionization of He and two-electron ions by high energy photons Miron Ya. Amusia, Evgenii G. Drukarev and Evgeny Z. Liverts Eur. Phys. J. D, 74 8 (2020) 173 Published online: 25 August 2020 DOI: 10.1140/epjd/e2020-10226-1