Chaotic enhancement in microwave ionization of Rydberg atoms

The microwave ionization of internally chaotic Rydberg atoms is studied analytically and numerically. The internal chaos is induced by magnetic or static electric fields. This leads to a chaotic enhancement of microwave excitation. The dynamical localization theory gives a detailed description of the excitation process even in a regime where up to few thousands photons are required to ionize one atom. Possible laboratory experiments are also discussed.