Breaking time reversal symmetry in chaotic driven Rydberg atoms

We consider the dynamics of Rydberg states of the hydrogen atom driven by a microwave field of elliptical polarization, with a possible additional sta tic electric field. We concentrate on the effect of a resonant weak field-w hose frequency is close to the Kepler frequency of the electron around the nucleus-which essentially produces no ionization of the atom, but completel y mixes the various states inside an hydrogenic manifold of fixed principal quantum number. For sufficiently small fields, a perturbative approach (bo th in classical and quantum mechanics) is relevant. For some configurations of the fields, the classical secular motion (i.e., evolution in time of th e elliptical electronic trajectory) is shown to be predominantly chaotic. C hanging the orientation of the static field with respect to the polarizatio n of the microwave field allows us to investigate the effect of generalized time-reversal symmetry breaking on the statistical properties of energy le vels. (C) 2000 Academic Press.