10min:

ANASTASIA DROZDOVA AND AMANDA J. ROSS, LASIM, Université Lyon 1 & CNRS, 43 Bd du 11 novembre 1918, F-69622 Villeurbanne, France ; ANDREY V. STOLYAROV, Department of Chemistry, Moscow State University, 119992 Moscow, Russia ; WLODZIMIERZ JASTRZEBSKI, Institute of Physics, Polish Academy of Sciences, Al. Lotnikóv 32/46, 02-668 Warsaw, Poland ; AND PAWE\L KOWALCZYK, Institute of Experimental Physics, Warsaw University, ul. Hoza 69, 00-681 Warsaw, Poland.

Two-colour polarization labeling experiments measuring the D X system of NaK have characterised more than 99 % of the potential well of the D~¹ state of NaK, the last observed level being located 7 cm^-1 below the Na(3p ²P_3/2) + K(4s) atomic asymptote. The vibrational progressions all exhibit irregular intervals, because of strong interactions with the nearby d ³ state. A comprehensive analysis has now been made of all available data concerning the D~¹ and d~³ states. The potential curves are represented by Morse/Lennard Jones analytical functions, with ab initio constraints on the long-range part of V(R). Morse functions are also used to represent the R-dependent diagonal and off-diagonal spin-orbit terms. Initial values for the spin-orbit coupling matrix elements were extracted from quasi-relativistic ab initio calculations. In total, 29 parameters were required to recalculate 95~% of the 1400 observed term energies to within experimental uncertainty, giving an unweighted standard deviation 0.03 cm^-1.