Spectral aspects of the microwave ionization of atomic Rydberg states

We perform a numerical study of the microwave ionization of a Rydberg state of atomic hydrogen, on the grounds of a one-dimensional model of the atom. Our work unifies, for the first time, all the different approaches to the microwave problem realized up to date, additionally taking into account the coupling to the continuum. This allows for an unambiguous identification of structures in the level dynamics with the observed ionization probability, as well as for testing the correlation between the electronic density distribution and the lifetime of individual eigenstates. Special emphasis is given to the sensitivity of the quasienergy spectrum with respect to changes of an external parameter, which seems a good candidate for a general characterization of quantal chaotic systems. The impact on experimental results is discussed, notably by stressing the important role of the experimental interaction time.