Strong-field approximation for intense-laser-atom processes: The choice of gauge

@article{Bauer2005StrongfieldAF,
  title={Strong-field approximation for intense-laser-atom processes: The choice of gauge},
  author={Dieter Bauer and Dejan B. Milo{\vs}evi{\'c} and Wilhelm Becker},
  journal={Physical Review A},
  year={2005},
  volume={72},
  pages={1-5}
}
The strong-field approximation (SFA) can be and has been applied in both length gauge and velocity gauge with quantitatively conflicting answers. For ionization of negative ions with a ground state of odd parity, the predictions of the two gauges differ qualitatively: in the envelope of the angular-resolved energy spectrum, dips in one gauge correspond to humps in the other. We show that the length-gauge SFA matches the exact numerical solution of the time-dependent Schr\"odinger equation. 
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