The origin of Λ-doubling effect for the B 1∏ and D 1∏ states of NaK

Abstract

The origin of Λ-doubling effect (q factors) for the regularly perturbed NaK B 1∏ and D 1∏ states has been investigated by means of ab initio many-body multipartitioning perturbation theory calculation of the electronic L-uncoupling matrix elements between the examined ∏1 and five lowest ∑+1 states for both Na3923K and Na4123K isotopomers. The hypothesis of pure precession was found to be valid for the B 1∏–A 1∑+ and D 1∏–C 1∑+ pairs of the interacted states, while the unique perturber approximation works properly for the D 1∏ state and completely breaks down for the B 1∏ state. The theoretical rovibronic q-factor values estimated for both states by means of the approximate sum rule agree well with their experimental counterparts and demonstrate high sensitivity to vibrational and rotational quantum numbers.