An ultracold heavy Rydberg system formed from ultra-long-range molecules bound in a stairwell potential

F Hummel,H Ott,H R Sadeghpour,P Schmelcher

doi:10.1088/1367-2630/ab90d7

Abstract

We propose a scheme to realize a heavy Rydberg system (HRS), a bound pair of oppositely charged ions, from a gas of ultracold atoms. The intermediate step to achieve large internuclear separations is the creation of a unique class of ultra-long-range Rydberg molecules bound in a stairwell potential energy curve. Here, a ground-state atom is bound to a Rydberg atom in an oscillatory potential emerging due to attractive singlet p-wave electron scattering. The utility of our approach originates in the large electronic dipole transition element between the Rydberg and the ionic molecule, while the nuclear configuration of the ultracold gas is preserved. The Rabi coupling between the Rydberg molecule and the heavy Rydberg system is typically in the MHz range and the permanent electric dipole moments of the HRS can be as large as one kilo-Debye. We identify specific transitions which place the creation of the heavy Rydberg system within immediate reach of experimental realization.

Highlights

A bound pair of oppositely charged ions can be viewed as the molecular analogue of an atomic Rydberg state in which the electron is replaced by the negatively charged anion, termed a heavy Rydberg system (HRS) [1, 2]
Formation of HRS via coupling to covalent Rydberg states in the long range in an ultracold environment has several advantages: because these states may form away from the complicated short-range molecular interaction region, there’s better control over their formation and spectroscopy; the decay channels which mainly consist of mutual neutralization into atomic species is greatly suppressed [10]; and the possibility that the ion pair constituents are both at ultracold temperatures and may lead to formation of a two-component strongly coupled plasma
We show that ultra-long-range Rydberg molecules can be used to produce ultracold heavy Rydberg system i.e. a bound anion-cation pair

Summary

Introduction

A bound pair of oppositely charged ions can be viewed as the molecular analogue of an atomic Rydberg state in which the electron is replaced by the negatively charged anion, termed a heavy Rydberg system (HRS) [1, 2]. Such HRS do form in ionic molecules, such as alkali-halides [3], and whose vibrational energy spectra follow the Rydberg quantum defect formula, R∞ Eν = − μ(ν δ) , (1).

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Conclusion