Rydberg electron-atom scattering in forbidden regions of negative kinetic energy

Abstract

Scattering of a Rydberg electron by ground-state atoms (scatterers) located in its classically forbidden region can be viewed as electron-atom scattering with negative incident energy. We propose a treatment of this unusual case of scattering in the context of long-range molecular potentials arising from the interaction of a Rydberg electron with ground state atoms. We describe a treatment leading to proper equivalents of scattering lengths and phase shifts for negative incident energies, which becomes advantageous when a Rydberg atom is penetrated by more than one scatterer and the Rydberg electron scatters back and forth between the atoms in the classically allowed and forbidden regions. We apply this approach to Cs and Rb samples, and find evidence for a resonance-like feature for their 3S1 states.