Production of rovibronic-ground-state RbCs molecules via two-photon-cascade decay

Abstract

We report the production of ultracold RbCs molecules in the rovibronic ground state, i.e., $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+}(v=0,J=0)$, by short-range photoassociation to the $2{\phantom{\rule{0.16em}{0ex}}}^{3}{\ensuremath{\Pi}}_{0}$ state followed by spontaneous emission. We use narrow-band depletion spectroscopy to probe the distribution of rotational levels formed in the $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+}(v=0)$ state. We conclude, based on selection rules, that the primary decay route to $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+}(v=0)$ is a two-step cascade decay that leads to as much as $33%$ branching into the $J=0$ rotational level. The experimental simplicity of our scheme opens up the possibility of easier access to the study and manipulation of ultracold heteronuclear molecules in the rovibronic ground state.