Hyperfine, rotational and Zeeman structure of the lowest vibrational levels of the $^{87}$Rb$_2$ $\tripletex$ state

TL;DR

This study combines experimental laser spectroscopy and theoretical modeling to analyze the detailed hyperfine, rotational, and Zeeman structures of the lowest vibrational levels of the $^{87}$Rb$_2$ $ ripletex$ state, revealing complex splitting patterns.

Contribution

It provides the first detailed experimental and theoretical characterization of the hyperfine, rotational, and Zeeman structures of the $^{87}$Rb$_2$ $ ripletex$ state for vibrational levels up to $v'=15$.

Findings

Resolved hyperfine, rotational, and Zeeman structures of the spectrum.

Identified a 47 GHz splitting dominated by second order spin-orbit interaction.

Described the spectral structure using a simplified effective Hamiltonian.

Abstract

We present the results of an experimental and theoretical study of the electronically excited $\tripletex$ state of $^{87}$Rb$_2$ molecules. The vibrational energies are measured for deeply bound states from the bottom up to $v'=15$ using laser spectroscopy of ultracold Rb$_2$ Feshbach molecules. The spectrum of each vibrational state is dominated by a 47\,GHz splitting into a $\cog$ and $\clg$ component caused mainly by a strong second order spin-orbit interaction. Our spectroscopy fully resolves the rotational, hyperfine, and Zeeman structure of the spectrum. We are able to describe to first order this structure using a simplified effective Hamiltonian.