2-DIMENSIONAL QUANTUM HYDROGEN-ATOM IN CIRCULARLY-POLARIZED MICROWAVES - GLOBAL PROPERTIES

The ionization of hydrogen Rydberg atoms by circularly polarized micro waves is studied quantum mechanically in a model two-dimensional atom. We apply a combination of a transformation to the coordinate frame ro tating with the field, with complex rotation approach and representati on of the atomic subspace in a Sturmian-type basis. The diagonalizatio n of resulting matrices allows us to treat exactly the ionization of a toms initially prepared in highly excited Rydberg states of principal quantum number n(0) approximate to 60. Similarities and differences be tween ionization by circularly and linearly polarized microwaves are d iscussed with a particular emphasis on the high-frequency regime and o n the localization phenomenon. The dependence of the ionization charac ter on the initial state (circular, elliptical, or low angular momentu m state) as well as on the helicity of the polarization is discussed i n detail. It is shown that, in the high-frequency chaotic regime, clos e encounters with the nucleus do not play a major role in the ionizati on process.