Excitation ionization and double ionization of helium by high-energy photon impact.

@article{Andersson1993ExcitationIA,
  title={Excitation ionization and double ionization of helium by high-energy photon impact.},
  author={C Andersson and Burgd{\"o}rfer},
  journal={Physical review letters},
  year={1993},
  volume={71 1},
  pages={50-53}
}