Orbital dynamics of two-electron atoms in a static electric field probed by scaled energy spectroscopy

Photoabsorption spectra for Ba and Ca Rydberg atoms are measured as a continuous function of electric field strength and electron energy. In both Ba and Ca, the singly-excited $msnd$ series are strongly perturbed by doubly-excited configurations. Using scaled energy recurrence spectroscopy, we investigate the dynamical signatures associated with the spectral variations observed in perturbed Rydberg series, namely oscillator strength modulation and energy-dependent quantum defects. In Ca, small shifts in the Kepler period, conspicuous at large action are attributed to the broad $3d5s$ and $3d3d$ perturbing resonances. In Ba, splittings in the primary recurrence peaks are observed only if the recurrence spectra are measured at energies near the narrow $5d7d$ perturber. These splittings reflect the time delay between electron scattering into and back out of the doubly-excited configuration and are consistent with measurements by Bates \textit{et al.}[Phys. Rev. A \textbf{64}, 033409 (2001)]. Our observations suggest that, in general, the dynamical consequences of interactions between low angular momentum. This work has been supported by the NSF.