Hyperfine structures of the $B^{\mathrm{1}}\Pi $, $c^{\mathrm{3}}\Sigma ^{\mathrm{+}}$, and $b^{\mathrm{3}}\Pi $ states of ultracold$^{\mathrm{\thinspace 85}}$Rb$^{\mathrm{133}}$Cs via short range photoassociation

Short-range photoassociation (PA) has opened up to investigate various hyperfine structures of deeply bound rovibrational levels of the strongly perturbed $B^{\mathrm{1}}\Pi $, $c^{\mathrm{3}}\Sigma^{\mathrm{+}}$, and $b^{\mathrm{3}}\Pi $ states with high resolution of \textasciitilde 10 MHz. Peculiar potential curves of the electronic states with crossings and inflections obtained from Fourier-transform spectroscopy (FTS) with low resolution of 900 MHz [1] give strong evidences for strong spin-orbit coupling effects between the singlet and triplet states. We have observed new short-range PA lines of the $B^{\mathrm{1}}\Pi (\Omega =$1), $b^{\mathrm{3}}\Pi (\Omega =0^{-}$, 0$^{\mathrm{+}}$, and 1), and 3$^{\mathrm{3}}\Sigma^{\mathrm{+}}(\Omega =0^{-}$and 1) states of ultracold $^{\mathrm{85}}$Rb$^{\mathrm{133}}$Cs molecule, starting with $^{\mathrm{85}}$Rb and $^{\mathrm{133}}$Cs atoms trapped in their \textbar F$_{\mathrm{Rb}}=$2\textgreater and \textbar F$_{\mathrm{Cs}}=$3\textgreater hyperfine states in dark SPOT MOTs. We have observed rich hyperfine structures of the $B^{\mathrm{1}}\Pi $, $c^{\mathrm{3}}\Sigma^{\mathrm{+}}$, and $b^{\mathrm{3}}\Pi $ states with $\Omega =$ 1, which were not observed in the FTS [1]. We will discuss the various hyperfine structures in comparisons with the hyperfine structures observed in PA to the 2$^{\mathrm{3}}\Pi (\Omega =$ 1), 2$^{\mathrm{1}}\Pi (\Omega =$ 1), and 3$^{\mathrm{3}}\Sigma ^{\mathrm{+}}(\Omega =$ 1) states [2]$\cdot $ [1] I. Birzniece \textit{et al}., J. Chem. Phys. \textbf{138}, 154304 (2013). [2] T. Shimasaki \textit{et al}., ChemPhysChem \textbf{17}, 3677 (2016).