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

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.Comment: 10 pages, 7 figures, 2 table