Exploring the vibrational series of pure trilobite Rydberg molecules

TL;DR

This paper reports the observation of two vibrational series in pure trilobite rubidium Rydberg molecules, demonstrating harmonic behavior, extreme properties, and potential for studying electron-atom interactions and molecular dynamics.

Contribution

First observation of vibrational series in pure trilobite Rydberg molecules with harmonic behavior, enabling new insights into electron-atom scattering and molecular wave dynamics.

Findings

Vibrational series are more than 15 GHz below the 22F state.

Vibrational states exhibit harmonic oscillator behavior.

Molecules have kilo-Debye dipole moments and long lifetimes.

Abstract

We report on the observation of two vibrational series of pure trilobite rubidium Rydberg molecules. They are created via three-photon photoassociation and lie energetically more than 15 GHz below the atomic 22$F$ state of rubidium. In agreement with theoretical calculations, we find an almost perfect harmonic oscillator behavior of six vibrational states. We show that these states can be used to measure electron-atom scattering lengths for low energies in order to benchmark current theoretical calculations. The molecules have extreme properties: their dipole moments are in the range of kilo-Debye and the electronic wave function is made up of high angular momentum states with only little admixture from the nearby 22$F$ state. This high-$l$ character of the trilobite molecules leads to an enlarged lifetime as compared to the 22$F$ atomic state. The observation of an equidistant series of vibrational states opens an avenue to observe coherent molecular wave-packet dynamics.