Laser Frequency-Modulated Spectroscopy of a Laser-Guided Plasma in Sodium Vapor: Line Positions for NaH (A1Sigma+-X1Sigma+), Na (9-13d and 11-14s), and Ar (5p-4s)

Dissociation energies and potential energy functions for the ground X (1)Σ(+) and "avoided-crossing" A (1)Σ(+) states of NaH

A direct-potential-fit analysis of all accessible data for the A (1)Σ(+) - X (1)Σ(+) system of NaH and NaD is used to determine analytic potential energy functions incorporating the correct theoretically predicted long-range behaviour. These potentials represent all of the data (on average) within the experimental uncertainties and yield an improved estimate for the ground-state NaH well depth of 𝔇e = 15797.4 (±4.3) cm(-1), which is ∼20 cm(-1) smaller than the best previous estimate. The present analysis also yields the first empirical determination of centrifugal (non-adiabatic) and potential-energy (adiabatic) Born-Oppenheimer breakdown correction functions for this system, with the latter showing that the A-state electronic isotope shift is -1.1(±0.6) cm(-1) going from NaH to NaD.

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.