Long-Range Wells in Rydberg-Rydberg Potential Curves

Michal Tarana, Roman vCur 'ik

Jovica Stanojevic, Robin C ot 'e

Nolan Samboy, Robin Côté

We explore long-range interactions between two atoms excited into high principal quantum number n Rydberg states, and present calculated potential energy curves for various symmetries of doubly excited n s and n p rubidium atoms. We show that the potential curves for these symmetries exhibit deep (∼ GHz) potential wells, which can support very extended (∼ µm) bound vibrational states ( macrodimers ). We present n -scaling relations for both the depth D e of the wells and the equilibrium separations R e of these macrodimers, and explore their response to small electric fields and stability with respect to predissociation. Finally, we present a scheme to form and study these macrodimers via photoassociation, and show how one can probe the various ℓ-character of the potential wells.

Jovica Stanojevic, Robin Côté, D. Tong +3 more

Aileen A. T. Durst, Milena Simić, Neethu Abraham +1 more

Long-range Rydberg molecules are typically bound in wells formed in their oscillatory potential energy curves. In alkaline Rydberg molecules, bound vibrational states exist even when these potential wells are disrupted by level repulsion from the steep butterfly potential energy curve induced by a scattering shape resonance. The binding in this case is attributed to quantum reflection. However, the rapidly varying regions of the potential energy landscape where quantum reflection occurs often coincide with regions where nonadiabatic coupling becomes significant. By comparing the molecular states calculated within the Born-Oppenheimer approximation, where quantum reflection is the only binding mechanism, with those obtained from the full set of coupled channel equations, we assess the effects of nonadiabatic coupling on vibrational energies and lifetimes. Our findings show that these couplings can stabilize the molecule by providing an additional barrier which protects the vibrational states from predissociation and nonradiative transitions. There can also be extreme cases where nonadiabatic coupling completely dominates the binding and the molecular lifetimes saturate at the atomic Rydberg lifetime.

Michael Peper, Jakob Skrotzki, Martin Trautmann +2 more

Long-range Rydberg molecules (LRMs) form when a highly excited Rydberg electron scatters from ground-state atoms inside its orbit, creating oscillatory, long-range potentials. We present a combined theoretical and experimental study of caesium dimers correlated to 402P3/2 Rydberg states, with an emphasis on decay via autoionisation (associative ionisation). Our model includes a relativistic treatment of electron-atom scattering with spin-orbit coupling, the perturber's hyperfine structure, and coupling of vibrational levels to a continuum of short-range decay channels. Calculated potential-energy curves predict two families of wells: outer wells near the classical outer turning point supporting long-lived states, and inner wells at shorter range whose lifetimes are limited by tunneling and subsequent vibronic decay. Using photoassociation in an ultracold Cs gas and an analysis of pulsed-field-ionisation signals which are highly selective for the detection of molecules, we assign resonances by binding energy and measure lifetimes. The measured lifetimes of inner-well states increase systematically with increasing detuning and agree with calculated lifetimes; detection of Cs2+ product ions supports autoionisation as a dominant channel. We show that the lifetimes are strongly reduced by spin-orbit interactions in the transient Cs-collision complex, which lift the near-degeneracy in Omega observed for states in the outer well and control the inner-well binding. The identified states also provide promising pathways to create ultracold molecules in ion-pair states.