2D Quantum Hydrogen Atom in Circularly Polarized Microwaves

The ionization of hydrogen Rydberg atoms by circularly polarized microwaves is studied quantum mechanically in a model two dimensional atom. We apply a combination of a transformation to the coordinate frame rotating with the field, with complex rotation approach and representation of atomic subspace in Sturmian-type basis. The diagonalization of resulting matrices allows us to treat exactly the ionization of atoms initially prepared in highly excited Rydberg states of principal quantum number $n_0\approx 60$. Similarities and differences between ionization by circularly and linearly polarized microwaves are discussed with a particular emphasis on the localization phenomenon. The dependence of the ionization character on the type of the initial state (circular, elliptical or low angular momentum state) as well as on the helicity of the polarization is discussed in detail.