Recurrence spectra of non-hydrogen Rydberg atoms in parallel electric and magnetic fields

We present a new method for computing the recurrence spectra of n ≈ 40, m = 0 lithium Rydberg atoms in strong parallel external electric and magnetic fields. This method is based on an extended closed-orbit theory allowing the computation of the scattering of the electron by the ionic core. We pay particular attention to the scaling properties, which are extremely important for understanding the correspondence between classical and quantum mechanics. The spectra with a constant scaled electric field \tildeF = 0.01 and a scaled energy \varepsilon = -0.03 are recorded and compared with those of hydrogen obtained by the standard closed-orbit theory. The result shows that the additional strong resonance structures can be interpreted in terms of the core-scattered classical closed orbits.