Scaled-Energy Spectroscopy of Helium and Barium Rydberg Atoms in External Fields

Abstract

and which at low field strength is responsible for the mixing of angular momentum states (r is the radius of the electron orbit). When diamagnetism dominates only two conserved quantities (energy W and z-component of angular momentum l) exist for this system with three spatial degrees of freedom, a prerequisite for chaos in classical physics. The diamagnetic effect not only becomes important for large values of B, but also for large values of r. As the radius r scales as (n is principal quantum number) it follows that the diamagnetic effect grows with so that in highly-excited states it may be studied at relatively moderate magnetic field strengths. The classically chaotic regime in the hydrogen atom is reached when the Lorentz force exerted by the field on the electron about equals the Coulomb force binding the electron. In the hydrogen ground state this condition can only be fulfilled for the huge field strength of Tesla, whereas in a Rydberg state with a field of 0.60 Tesla suffices. This, together with the fact that the hydrogen atom is experimentally not easily accessible, constitutes the major argument to investigate this effect also in Rydberg states of more complex atoms. An additional point of interest then relates to the influence of an extended atomic core, represented by a quantum defect in regular Rydberg sequences, on the observed spectra in the presence of a magnetic field. Similar arguments hold for the investigation of Rydberg states in the presence of an external electric field E. Now it is the linear Stark effect, that at moderate field strengths induces mixing of angular momentum l-states, reflected in the appearance of angular momentum manifolds in the spectra, and at high field strengths also mixing of n-states. Finally field ionization will occur in sufficiently strong fields. In Rydberg states the sensitivity for electric fields is again strongly enhanced. In contrast to the