Experimental Studies of the 4$^3\Pi$ Electronic State of NaCs

We present results from experimental studies of the 4$^3\Pi$ electronic state of the NaCs molecule. This electronic state is interesting in that its potential energy curve likely exhibits a double minimum. As a result, interference effects are observed in the resolved bound-free fluorescence spectra. The optical-optical double resonance method was used to obtain Doppler-free excitation spectra for the 4$^3\Pi$ state. This dataset of measured level energies was expanded largely by observing fluorescence from levels populated by collisions. Simulations of resolved bound-free fluorescence spectra were calculated using the BCONT program (R. J. Le Roy, University of Waterloo). Spectroscopic constants are presented as a preliminary step toward an experimental potential energy curve.