Long-Range Atom–Ion Rydberg Molecule: A Novel Molecular Binding Mechanism

Markus Deiß,Johannes Hecker Denschlag,Shinsuke Haze

doi:10.3390/atoms9020034

Abstract

We present a novel binding mechanism where a neutral Rydberg atom and an atomic ion form a molecular bound state at a large internuclear distance. The binding mechanism is based on Stark shifts and level crossings that are induced in the Rydberg atom due to the electric field of the ion. At particular internuclear distances between the Rydberg atom and the ion, potential wells occur that can hold atom–ion molecular bound states. Apart from the binding mechanism, we describe important properties of the long-range atom–ion Rydberg molecule, such as its lifetime and decay paths, its vibrational and rotational structure, and its large dipole moment. Furthermore, we discuss methods of how to produce and detect it. The unusual properties of the long-range atom–ion Rydberg molecule give rise to interesting prospects for studies of wave packet dynamics in engineered potential energy landscapes.

Highlights

IntroductionThe sign flip of the polarizability goes along with an avoided crossing between a low-field-seeking and a high-field-seeking energy level of the Rydberg atom, both of which experience individual Stark shifts in the electric field of the ion
Molecular Binding Mechanism.Molecules or bound complexes are often classified according to their binding mechanisms
A Rydberg atom is bound to an ion at a large given internuclear distance, which clearly exceeds the extension of the Rydberg electron wave function

Summary

Introduction

The sign flip of the polarizability goes along with an avoided crossing between a low-field-seeking and a high-field-seeking energy level of the Rydberg atom, both of which experience individual Stark shifts in the electric field of the ion. For such an avoided crossing, the upper branch forms a potential well, which can exhibit molecular bound states. For the long-range atom–ion Rydberg molecule predicted here, we show that a Rydberg series of bound states exists, within which the binding energies and bond lengths strongly vary. An observation of the proposed long-range atom–ion Rydberg molecule may be possible in the near future

Binding Mechanism and Properties of the Long-Range Atom–Ion Rydberg

Stability and Lifetime of the Long-Range Atom–Ion Rydberg Molecules

Production by Photoassociation

Detection by Photoionization

Prospects for Experiments with Long-Range Atom–Ion Rydberg Molecules

Conclusions and Outlook