Charged ultralong-range Rydberg trimers

TL;DR

This paper predicts the existence of charged ultralong-range Rydberg trimers formed by a Rydberg atom, an ion, and a ground state atom, with unique electronic structures and binding energies detectable by current experiments.

Contribution

It introduces the concept of charged ultralong-range Rydberg trimers and analyzes their electronic and vibrational structures using advanced computational methods.

Findings

Identification of two families of ion-Rydberg molecular states

Prediction of bound trimers with linear and nonlinear configurations

Distinct binding energies and excitation series from ion-Rydberg dimers

Abstract

We show that the recently observed class of long-range ion-Rydberg molecules can be divided into two families of states, which are characterised by their unique electronic structures resulting from the ion-induced admixture of quantum defect-split Rydberg $n$P states with different low-field seeking high-$l$ states. We predict that in both cases these diatomic molecular states can bind additional ground state atoms lying within the orbit of the Rydberg electron, thereby forming charged ultralong-range Rydberg molecules (ULRM) with binding energies similar to that of conventional non-polar ULRM. To demonstrate this, we consider a Rydberg atom interacting with a single ground state atom and an ion. The additional atom breaks the system's cylindrical symmetry, which leads to mixing between states that would otherwise be decoupled. The electronic structure is obtained using exact diagonalisation over a finite basis and the vibrational structure is determined using the Multi-Configuration Time-Dependent Hartree method. Due to the lobe-like structure of the electronic density, bound trimers with both linear and nonlinear geometrical configurations of the three nuclei are possible. The predicted trimer binding energies and excitation series are distinct enough from those of the ion-Rydberg dimer to be observed using current experimental techniques.