Modelling by maps of the two-frequency microwave ionization of hydrogen atoms

Mapping equations of motion of the highly excited classical atom in a monochromatic field are generalized for the two-frequency microwave field. The analysis of the obtained equations shows the weak sensitivity of the position of the recently observed ionization peak near the main resonance to the frequency and amplitude of the additional microwave field. In the high-frequency region, however, the sensitivity of the enhanced ionization peaks on the additional field frequency is predicted