Rydberg atom-ion collisions in cold environments

Henrik Hirzler,Jesús Pérez-Ríos

doi:10.1103/physreva.103.043323

Abstract

Low-energy collisions of Rydberg atom-ion systems are investigated theoretically. We present the parameter space associated with suitable approaches for the dynamics of Rydberg atom-ion collisions, i.e. quantum-, Langevin and classical exchange regimes, showing that for the lowest reachable temperatures a classical treatment is appropriate. A quasi-classical trajectory method is used to study charge exchange cross sections for Li$^*$-Li$^+$ and Li$^*$-Cs$^+$ at collision energies down to $1\,$K. For cold collisions we find the charge exchange cross section deviating from the $n^4$ geometric scaling. Furthermore, for low-energy collisions, we find both an influence of the ionic core-repulsion as well as variations for two different models used for describing the electron-core potential.

Highlights

More than a century ago, after systematically studying atomic spectral lines, Rydberg gave a glimpse into the intriguing physics of highly excited states of atoms, nowadays known as Rydberg states [1]
We present the parameter space associated with suitable approaches for the dynamics of Rydberg atom-ion collisions, i.e., quantum, Langevin, and classical exchange regimes, showing that for the lowest reachable temperatures a classical treatment is appropriate
For cold collisions we find the charge exchange cross section deviating from the n4 geometric scaling

Summary

INTRODUCTION

More than a century ago, after systematically studying atomic spectral lines, Rydberg gave a glimpse into the intriguing physics of highly excited states of atoms, nowadays known as Rydberg states [1]. Models were extended with tailored pseudopotentials accounting for the role of core electrons in the Rydberg atom and ion, which allowed one to calculate the state changing collision cross section after binning the classical phase space at the final propagation time [34]. None of these theoretical approaches explored the nature of the charge-transfer process between an ion and a Rydberg atom at cryogenic and low temperatures. We find that for typical temperatures for BoseEinstein condensation (∼100 nK), Rydberg-ion collisions are satisfactorily described from a classical framework

A PHASE DIAGRAM FOR SCATTERING METHODS ON ION-RYDBERG COLLISIONS

THEORETICAL APPROACH

RESULTS

SUMMARY AND CONCLUSIONS