Ionization of magnesium atoms in femtosecond 400-nm laser fields

Atomic magnesium (Mg) is reported to ionize more efficiently in 400-nm laser fields with circular polarization (CP) than with linear polarization. This experimental result is reproduced qualitatively by numerical solutions of a two-electron time-dependent Schr??dinger equation. Theoretical analyses show that intermediate excited states play an important role during the ionization process. The 3s3p state and the 3s3d state are identified as the dominant intermediate states. The main ionization pathway is identified to be 3s2 -* 3s3p -* 3s3d -* ionized states. CP laser fields are shown to be able to pump more population from the ground state to the 3s3d state, leading to more efficient ionization of the Mg atoms.