Long-range potentials and $(n-1)d+ns$ molecular resonances in an ultracold rydberg gas

TL;DR

This paper calculates long-range molecular potentials of rubidium Rydberg atoms to understand resonances involving $(n-1)d+ns$ states, revealing how Rydberg interactions enable otherwise forbidden molecular transitions.

Contribution

It provides detailed calculations of molecular potentials and resonance lineshapes, explaining the origin of specific long-range molecular resonances in ultracold rubidium gases.

Findings

Identification of molecular potentials relevant to Rydberg interactions

Explanation of $ ext{l}$-mixing effects enabling forbidden transitions

Agreement between calculated and experimental resonance lineshapes

Abstract

We have calculated long-range molecular potentials of the $0_g^{+}$, $0_u^{-}$ and $1_u$ symmetries between highly-excited rubidium atoms. Strong $np+np$ potentials characterized by these symmetries are important in describing interaction-induced phenomena in the excitation spectra of high $np$ Rydberg states. Long-range molecular resonances are such phenomena and they were first reported in S.M. Farooqi {\it et al.}, Phys. Rev. Lett. {\bf 91} 183002. One class of these resonances occurs at energies corresponding to excited atom pairs $(n-1)d+ns$. Such resonances are attributed to $\ell$-mixing due to Rydberg-Rydberg interactions so that otherwise forbidden molecular transitions become allowed. We calculate molecular potentials in Hund's case (c), use them to find the resonance lineshape and compare to experimental results.