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.

Theoretical study of spin–orbit and Coriolis coupling among the low-lying states of Rb2 and Cs2

“…The spin-averaged and spin-orbit Gaussian basis sets used for each atom were borrowed from the above references. The shape-consistent ECPs were augmented by diffuse part of the all-electron bases for electric property calculation [30] and extended by additional diffuse and polarization functions [31,32,33]. The difference of results obtained by the above ECP basis sets is found not to exceed few percents except the R-region of small internuclear distances.…”

Λ-Doubling investigation of the 51Πg Rydberg state of Na2 using optical–optical double resonance spectroscopy

“…Using second-order non-degenerate perturbation theory [9], this increases quadratically with rotational quantum number J as D ef/P = q vJ/P [J(J + 1) À K 2 ]. The expression for q vJ/P takes the form…”

“…To analyze the K-doubling splitting, the regular perturbation is applied by coupling the state of interest to the nearby electronic states whose K value differs by one [6]. The observations of K-doubling have been reported for molecules such as, NO, H 2 , Li 2 , and NaK [7,8,9]. In the sodium dimer, K-doubling has been reported only in the B 1 P u state with the first-order splitting constant q 0 = 0.115 · 10 À4 cm À1 .…”

Investigation of the D 1Π state of NaK by polarisation labelling spectroscopy

“…[6]. They were assumed to extrapolate reasonably to higher vibrational levels; q v does decrease with increasing vibrational quantum number, as the ab initio predictions of Adamson et al [7] suggest they should (no quantitative predictions were given in the ab initio work). Following the convention of Ref.…”

“…Tamanis and co-workers [6] have studied the K-doubling in low-lying excited states of NaK, using argon ion laser lines to excite the molecule in the presence of a scanning radio-frequency electric field (radio-frequency + optical double resonance), showing that the K-doubling in the D 1 P state may be attributed to interactions with the lowerlying C 1 R + state only. The origin of the K-doubling in the two lowest 1 P states (B 1 P and D 1 P) was successfully modelled by the ab initio electronic structure calculations of Adamson and coworkers [7]. A careful deperturbation of the rotational structure observed in some levels of the D 1 P $ d 3 P complex has been published by Pazyuk and co-workers [8], covering vibrational levels v = 2-18 in the singlet state.…”