Production of rovibronic ground-state $^{85}$Rb$^{133}$Cs molecules via photoassociation to $\Omega=1$ states

We have extensively investigated short-range photoassociation (PA) to the $(2)^3\Pi_1$, $(2)^1\Pi_1$, and $(3)^3\Sigma^+_1$ states of $^{85}$Rb$^{133}$Cs in the region between 11650 cm$^{-1}$ and 12100 cm$^{-1}$, where strong mixing between triplet and singlet states is expected. In contrast to the previously observed two-photon cascade decay from the $(2)^3 \Pi_0$ states \footnote{T. Shimasaki {\it et al.} Phys. Rev. A, 91, 021401(R)(2015)}, here we observe that the PA excited states can directly decay to the rovibronic ground state $X^1\Sigma^+ (v=0,J=0)$ by a one-photon transition. We have observed rich hyperfine structures of the PA states, which were unresolved in previous cold beam experiments in the same region \footnote{Y. Lee {\it et al.} J. Phys. Chem. A, 112, 7214(2008)}. Based on the analysis of vibrational and rotational branching ratios in the decay process to the $X^1\Sigma^+$ state, we will discuss the molecule production rate in comparison with that for PA to the $(2)^3 \Pi_0$ states. We will also report on a similar study of PA to the $B^1\Pi$ and $(2)^3 \Sigma^+_1$ states of $^{85}$Rb$^{133}$Cs, which also produce the rovibronic ground state $X^1\Sigma^+ (v=0,J=0)$ via direct one-photon decay.