The citation of the code employed in the presented calculations is to be added so that the first sentence of Sec. III should read as follows: The approximate Fock-space relativistic coupled-cluster method developed in Sec. II A was implemented on the top of the DIRAC15 program package [1] and employed to calculate adiabatic potential-energy curves E i (R) for the ground and low-lying excited states of RbCs and Cs 2 molecules.

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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.

The iron oxide ‘orange arc’ bands are unambiguously detected in persistent meteor trains, meteor wakes, and clouds, as well as in the terrestrial airglow. In contrast to the majority of other astronomically important diatomic molecules, theoretical simulation of the FeO rovibronic spectra is not feasible due to the extremely condensed and strongly perturbed multiplet structure of its excited states. In this work, the time-evolution of the laser-induced breakdown spectra (LIBS) of high-purity iron recorded in air at high temperature and impact conditions is used to mimic the FeO pseudo-continuum emission observed during meteor events and the terrestrial night airglow. The relative intensity distributions in the structural continuum of the LIBS spectra are measured at 530–660 nm and a plasma temperature of 1500–6500 K. The anomalous increase of the intensity observed at 620–640 nm and temperature < 2000 K could be attributed to the emission of higher oxides of iron as explained by the conducted thermodynamic and kinetic modeling of iron burning in the atmosphere.