An improved potential energy curve for the ground state of NaK

This paper presents an accurate potential curve for the ground state of the NaK molecule. A series of resolved laser-induced fluorescence spectra of t he A-X system allowed a spread of rotational levels in the lowest 70 vibrat ional levels (99.9% of the total well depth) to be observed. A variational method combining the inverted perturbation approach of Vidal and Scheingrab er (Vidal C R and Scheingraber H 1977 J. Mol. Spectrosc. 65 46) for short i nternuclear distances with an analytical expression for internuclear distan ces beyond 8.5 Angstrom has been used to construct a potential energy curve which reproduces the measured ground state energies with an rms error of 0 .003 cm(-1). The dissociation energy and coulombic parameters governing the Na(3s) + K(4s) interaction derived from this potential curve are compared with recent values.