Parity nonconservation effect in the resonance elastic electron   scattering on heavy He-like ions
  We investigate the parity nonconservation effect in the elastic scattering of polarized electrons on heavy He-like ions, being initially in the ground state. The enhancement of the parity violation is achieved by tuning the energy of the incident electron in resonance with quasidegenerate doubly-excited states of the corresponding Li-like ion. We consider two possible scenarios. In the first one we assume that the polarization of the scattered electron is measured, while in the second one it is not detected. 
V. A. Zaytsev, A. V. Maiorova, V. M. Shabaev, S. Tashenov, and Th.   Stoehlker
physics.atom-ph