ИСТИНА

Energetic and dynamic properties of rovibronic levels of electron-excited states can not be properly described without taking non-adiabatic interactions into account [1]. The non-adiabatic matrix elements (such as spin-orbit or L-coupling functions) can be computed using high level ab initio methods with an accuracy of 5-10 %. As a result, these ab initio matrix elements are widely used for modelling of energetic and dynamic properties and as an initial estimate for direct deperturbation treatment. In this work, we systematically investigate the influence of both homogeneous spin-orbit and heterogeneous electron-rotational interactions on the c 3 Σ + Ω state of the LiK, LiRb, and LiCs molecules using ab initio calculations. According to the selection rules [1], the c 3 Σ + state is perturbed by the 1 Π and 3 Π states. Their corresponding non- adiabatic matrix elements between states converging to the second and third dissociation limits are calculated as follows: The small-core effective core potentials (ECPs) with 9 electrons (1 valence + 8 subvalence) are used for K, Rb, and Cs while Li is described using an ECP with a single valence electron [2]. The internally contracted multi-reference configuration interaction (MRCI) method with preliminary state-averaged complete active space self-consistent field (SA-CASSCF) optimization is used to compute the potential energy curves as well as non- adiabatic matrix elements. Core polarization effects are taken into account using l-independent core polarization potentials (CPPs) [3]. It is found that electron-rotational effects are stronger than the spin-orbit effects in the case of LiK, have a same magnitude in the case of LiRb, and are much weaker in the case of LiCs. However, both interactions should be taken into account for a precise description of rovibronic level properties for each molecule. The energetic levels of the c 3 Σ + Ω state are affected with regular and local perturbations. For the regularly perturbed low-lying levels of c 3 Σ + the Van Vleck perturbation theory is applied to take interactions with the 1,3 Π states into Ω account while Ω-components of the state are treated explicitly using only the Coupled Channels method. On the other hand, strong local perturbations in the c 3 Σ + − b 3 Π crossing region are described using the Coupled Channels method. The study was funded by RFBR according to the research project N 18-33-00753. References [1] H. Lefebvre-Brion and R. W. Field, The Spectra and Dy- namics of Diatomic Molecules: Revised and Enlarged Edition, Academic Press, 2004. [2] M. M. Hurley, L. F. Pacios, P. A. Christiansen, R. B. Ross and W. C. Ermler, J. Chem. Phys., 84, 6840–6853 (1986). [3] W. Muller, J. Flesch and W. Meyer, J. Chem. Phys., 80, 3297–3310 (1984).