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Polarization effects in the total rate of biharmonic $ω+ 3ω$ ionization of atoms

The total ionization rate of biharmonic ($ω+ 3ω$) ionization is studied within the independent particle approximation and the third order perturbation theory. Particular attention is paid to how the polarization of the biharmonic light field affects the total rate. The ratios of the biharmonic ionization rates for linearly and circularly polarized beams as well as for corotating and counterrotating elliptically polarized beams are analyzed, and how they depend on the beam parameters, such as photon frequency or phase between $ω$ and $3ω$ light beams. We show that the interference of the biharmonic ionization amplitudes determines the dominance of a particular beam polarization over another and that it can be controlled by an appropriate choice of beam parameters. Furthermore, we demonstrate our findings for the ionization of neon $L$ shell electrons.