Electron-impact ionization of laser-excited sodium atom

We report the experimental results of the total electron-impact ionization cross sections of laser-excited 3P sodium in the energy range from threshold to 30 eV. These cross sections were measured simultaneously for both ground-state and 3P excited-state atoms as a function of electron-impact energy. Excited-state data were calibrated with respect to the ground-state data that were normalized to the recent Johnston and Burrow measurements [Phys. Rev. A 51, R1735 (1995)]. We find good general agreement with theory. However, the position of the maximum is almost the same as that predicted by the calculations employing generalized oscillator strengths based on the Born approximation, and is at a higher energy than that which the convergent close-coupling predicts.