Autoionization of an ultracold Rydberg gas through resonant dipole coupling

TL;DR

This study explores a resonant dipole coupling mechanism for autoionization in ultracold Rydberg gases, finding it unlikely to be a primary process but potentially a trigger for secondary ionization, with implications for complex many-body systems.

Contribution

It introduces a new mechanism based on long-range dipole interactions for autoionization in ultracold Rydberg gases, including multi-particle effects and atom motion.

Findings

Ionization rates are very low for the proposed mechanism.

Multi-particle systems can enhance ionization probability.

The process may trigger secondary ionization rather than cause primary autoionization.

Abstract

We investigate a possible mechanism for the autoionization of ultracold Rydberg gases, based on the resonant coupling of Rydberg pair states to the ionization continuum. Unlike an atomic collision where the wave functions begin to overlap, the mechanism considered here involves only the long-range dipole interaction and is in principle possible in a static system. It is related to the process of intermolecular Coulombic decay (ICD). In addition, we include the interaction-induced motion of the atoms and the effect of multi-particle systems in this work. We find that the probability for this ionization mechanism can be increased in many-particle systems featuring attractive or repulsive van der Waals interactions. However, the rates for ionization through resonant dipole coupling are very low. It is thus unlikely that this process contributes to the autoionization of Rydberg gases in the form presented here, but it may still act as a trigger for secondary ionization processes. As our picture involves only binary interactions, it remains to be investigated if collective effects of an ensemble of atoms can significantly influence the ionization probability. Nevertheless our calculations may serve as a starting point for the investigation of more complex systems, such as the coupling of many pair states proposed in [Tanner et al., PRL 100, 043002 (2008)].