Long-range potentials for the X¹Σ⁺ and a³Σ⁺ states of the NaK molecule

Abstract

Fluorescence spectra of the NaK molecule excited by the 4765 Å and 4880 Å lines of an argon-ion laser have been recorded at high resolution by Fourier-transform spectrometry. Constants for the ground state X ¹Σ⁺ and for the first excited state, a ³Σ⁺, have been determined from a simultaneous least-squares fit to a total of 1758 lines assigned to five systems. Rotationless potentials for these two states have been calculated at internuclear distances out to about 9·3 Å for the ground state and to about 9·1 Å for the triplet state. The dissociation energy, D _e (NaK), is found to be 5274·9 ± 0·5 cm^-1, and the long-range potential for X ¹Σ⁺ is given by

with V in cm^-1, r in Å. Values of the potential constants are in satisfactory agreement with the results of recent calculations.