Spin–orbit coupling and Λ doubling in NaAr

A b initio values of spin-orbit coupling constants and Λ-doubling parameters have been obtained for the A 2Πr state of NaAr. Values are in reasonable agreement with experiment and, in particular, suggest that calculated potentials may be used to account for the Λ-doubling, provided that a reasonable model is used. The interest in NaAr arises from the fact that the Λ-doubling parameters in the A 2Π state give direct information about the Na+Ar interaction in the B 2Σ+ state. The success of the fine structure calculations presented here encourages application of similar methods to other van der Waals species.