Experimental Studies of the NaCs $5^3\Pi_0$, $4^3\Pi_0$, and $1(a)^3\Sigma^+$ States

We present experimental studies of the NaCs molecule that are currently underway in our laboratory. The optical-optical double resonance method is used to obtain Doppler-free excitation spectra for several excited states. Selected data from the $5^3\Pi_0$ and $4^3\Pi_0$ electronic states are used to obtain Rydberg-Klein-Rees (RKR) and Inverse Perturbation Approach (IPA) potential curves. We have also mapped the repulsive wall of the $1(a)^3\Sigma^+$ potential using many resolved bound-free fluorescence spectra from individual ro-vibrational levels of the $5^3\Pi_0$ electronic state to the $1(a)^3\Sigma^+$ state. Using the determined $5^3\Pi_0$ state potential, we fit the repulsive wall of the $1(a)^3\Sigma^+$ state to reproduce the experimental spectra using LeRoy's BCONT program. A slightly modified version of BCONT is also used to fit the relative transition dipole moments, $\mu_e(R)$, as a function of internuclear separation R, for the various bound-free electronic transitions. We also present bound-free spectra and BCONT simulations for the nearby $4^3\Pi_0$ electronic state of NaCs.