Observation of spin singlet butterfly Rydberg molecules in an ultracold atomic Rb gas

TL;DR

This paper reports the first observation of spin-singlet butterfly Rydberg molecules in an ultracold Rb gas, demonstrating their binding energies, electric dipole moments, and lifetimes, aligning well with theoretical predictions.

Contribution

It introduces the experimental realization of spin-singlet butterfly Rydberg molecules using a three-photon excitation scheme in an ultracold Rb gas, a novel achievement in the field.

Findings

Observation of two long-lived vibrational levels.

Measured binding energies and electric dipole moments match theory.

Successful photoassociation via weakly admixing Rb states.

Abstract

We report the observation of spin-singlet ultra-long range Rydberg butterfly molecules consisting of a ground-state atom bound to a Rydberg atom by $P$-wave scattering of $^{87}$Rb Rydberg electrons from $^{87}$Rb(5s) atoms. A three-photon excitation scheme enables the photoassociation of these molecules by weakly admixing Rb($18f_{7/2}$) states. The measured binding energies, kilo-Debye permanent electric dipole moments, and lifetimes are in excellent agreement with theory. Two long-lived vibrational levels, red detuned from the Rb($18f_{7/2}$) threshold, are observed. This experiment is a foundational step in the production of ultra-cold anions and heavy Rydberg ion-pair systems.