The influence of a second active electron is studied in the high-order regime of nonrelativistic harmonic generation in model helium. The major deviation of the harmonic yield due to the second active electron is small and associated mostly with the descreening of the helium nucleus while only an even smaller part remains as a consequence of the electron-electron repulsion.

• Received 21 May 2001

DOI:https://doi.org/10.1103/PhysRevA.64.045402