Dissociation energy of the ground state of NaH.

The dissociation energy of the ground state of NaH was determined by analyzing the observed near dissociation rovibrational levels. These levels were reached by stimulated emission pumping and fluorescence depletion spectroscopy. A total of 114 rovibrational levels in the ranges 9<or=v(")<or=21 and 1<or=J(")<or=14 were assigned to the X (1)Sigma(+) state of NaH. The highest vibrational level observed was only about 40 cm(-1) from the dissociation limit in the ground state. One quasibound state, above the dissociation limit and confined by the centrifugal barrier, was observed. Determining the vibrational quantum number at dissociation v(D) from the highest four vibrational levels yielded the dissociation energy D(e)=15 815+/-5 cm(-1). Based on new observations and available data, a set of Dunham coefficients and the rotationless Rydberg-Klein-Rees curve were constructed. The effective potential curve and the quasibound states were discussed.