Dichroism in short-pulse two-color XUV plus IR multiphoton ionization of atoms

Circular and linear dichroism in the angular distributions of photoelectrons in multiphoton ionization of unpolarized atoms by a combination of two short pulses in the extreme ultraviolet (XUV) and infrared (IR) range is theoretically considered. A noticeable circular dichroism is predicted in the case when both XUV and IR pulses are circularly polarized. Here the dichroism may be observed not only in angle-resolved but also in angle-integrated experiments. When the XUV photons are linearly polarized while the IR pulses are circularly polarized, the circular dichroism can be observed only in angle-resolved experiments. In this case the dichroism averaged over a spectral line is small. When both pulses are linearly polarized, the photoelectron yield strongly depends on the angle between the polarizations, which leads to the considerable linear dichroism.