# Two-photon photoassociation spectroscopy of the $^{2}\Sigma^+$ YbLi molecular ground state

## TL;DR

This paper reports precise measurements of weakly bound states of ultracold YbLi molecules, analyzes the molecular potential, refines the interspecies scattering length, and demonstrates creation of atom-molecule superposition states, advancing ultracold molecule production.

## Contribution

It provides detailed spectroscopic data and theoretical analysis for YbLi molecules, improving understanding of their interactions and enabling efficient ultracold molecule formation.

## Key findings

- Measured binding energies of YbLi vibrational states
- Refined the interspecies s-wave scattering length to 30 a0
- Observed dark atom-molecule superposition states

## Abstract

We report on measurements of the binding energies of several weakly bound vibrational states of the paramagnetic $^{174}$Yb$^{6}$Li molecule in the electronic ground state using two-photon spectroscopy in an ultracold atomic mixture confined in an optical dipole trap. We theoretically analyze the experimental spectrum to obtain an accurate description of the long-range potential of the ground state molecule. Based on the measured binding energies, we arrive at an improved value of the interspecies $s$-wave scattering length $a_{s0}=30$ $a_0$. Employing coherent two-photon spectroscopy we also observe the creation of ''dark'' atom-molecule superposition states in the heteronuclear Yb-Li system. This work is an important step towards the efficient production of ultracold YbLi molecules via association from an ultracold atomic mixture.