High precision spectroscopy of trilobite Rydberg molecules

TL;DR

This study achieves high-resolution spectroscopy of trilobite Rydberg molecules, providing precise experimental data that benchmark and refine theoretical models, and extracting low-energy electron-atom scattering parameters with unprecedented accuracy.

Contribution

It presents the first high-resolution spectra of $^{87}$Rb trilobite molecules for multiple principal quantum numbers, and employs a new Green's function approach to accurately reproduce vibrational spectra.

Findings

High-resolution spectra of trilobite molecules obtained.

Theoretical models accurately reproduce vibrational spectra.

Precise measurement of low-energy electron-atom scattering phase shift.

Abstract

We perform three-photon photoassociation to obtain high resolution spectra of $^{87}$Rb trilobite dimers for the principal quantum numbers $n = 22,24,25,26$, and $27$. The large binding energy of the molecules in combination with a relative spectroscopic resolution of $10^{-4}$ provides a rigorous benchmark for existing theoretical models. A recently developed Green's function framework, which circumvents the convergence issues that afflicted previous studies,, is employed to theoretically reproduce the vibrational spectrum of the molecule with high accuracy. The relatively large molecular binding energy are primarily determined by the low energy $S$-wave electron-atom scattering length, thereby allowing us to extract the $^3S_1$ scattering phase shift with unprecedented accuracy, at low energy regimes inaccessible to free electrons.