  We theoretically study multiphoton ionization of Mg in the circularly as well
as the linearly polarized laser fields. Specifically two-, three-, and
four-photon ionization cross sections from the ground and first excited states
are calculated as a function of photon energy. Calculations are performed using
the frozen-core Hartree-Fock and also the model potential approaches and the
results are compared. We find that the model potential approach provide results
as good as or even slightly better than those by the frozen-core Hartree-Fock
approach. We also report the relative ratios of the ionization cross sections
by the circularly and linearly polarized laser fields as a function of photon
energy, which exhibit clear effects of electron correlations.
