Spectroscopic determination of the ground-state dissociation energy and isotopic shift of NaD

Stimulated emission pumping with fluorescence depletion spectroscopy is used to determine the NaD X ¹Σ⁺ ground-state dissociation energy and its isotopic shift. A total of 230 rovibrational levels in the range 9 ≤ v″ ≤ 29 and 1 ≤ J″ ≤ 11 are observed, where v″ = 29 is about 50 cm^-1 below the dissociation limit. Analysis of the highest five vibrational levels yields the dissociation energy D_e = 15 822 ± 5 cm^-1 with a vibrational quantum number at dissociation v_D = 31.2 ± 0.1. The energy difference in the well depth of this isotopologue with respect to that of NaH is δD_e = D_e(NaH) - D_e(NaD) = -7 cm^-1. A new set of Dunham coefficients is derived to fit all the observed energy levels to within the experimental uncertainty.