ИСТИНА

The correct behavior of intramolecular interaction matrix elements is of vital importance to the realization of laser cooling techniques such as photoassociation and stimulated Raman adiabatic passage (STIRAP), which have been actively utilized in recent years to investigate ultracold molecules. These techniques involve closed optical schemes with rovibronic levels of electron-excited states used as intermediate steps. Therefore, the search for efficient optical pathways requires a priori knowledge of the energetic and radiative properties of the intermediate electron excited states with a precision that goes beyond the adiabatic approximation, obtaining not only highly precise potential energy curves, but also non-adiabatic interaction matrix elements, particularly the spin-orbit (SO) and L-coupling matrix elements, in a wide range of interatomic distances. In this work, an investigation into the long-range behavior of intramolecular interaction matrix elements (IIMEs) xis presented, focusing on the transition-dipole moment (TDM) [1], spin orbit coupling (SOC)[2], and, in particular, the L-coupling (LC) matrix elements. The IIME functions are evaluated using spin-averaged wavefunctions corresponding to pure Hund’s coupling case (a) by means of effective core pseudopotentials. The electronic correlation is accounted for by applying the multi-reference configuration interaction (MRCI) method to only two valence electrons for all considered molecules and core-polarization potentials are used to take the core–valence effect into account. Additionally, the experimental [3,4] and theoretical data were compared, where available. The leading asymptotic trends for the TDMs, SOCs, and LCs, have been determined. The TDMs converge as a function of R-3, where R is the internuclear distance, to the atomic dipole moment. The SOC functions converge as a function of R-3 and R-6 to the atomic SO splitting, and zero, respectively, for interactions between states that converge to different and the same dissociation limit, respectively. The LC functions exhibit three different types of asymptotic behaviors (See Fig 1.): (a) they converge as a function of R-6 to a constant for couplings between states that converge to the same dissociation limit; (b) they converge to zero as a function of R-3 for forbidden transitions between states that converge to different dissociation limits; and (c) they approach infinity linearly for allowed transitions between states that converge to different dissociation limits. References [1] Ekaterina Bormotova, Sergey Kozlov, Elena Pazyuk, and Andrey Stolyarov. Long-range behavior of the transition dipole moments of heteronuclear dimers XY (X,Y = Li, Na, K, Rb) based on ab initio calculations. Phys. Chem. Chem. Phys. 20, 1889–1896 (2018). [2] E. A. Bormotova, S. V. Kozlov, E. A. Pazyuk, A. V. Stolyarov, W. Skomorowski, I. Majewska, and R. Moszynski. Ab initio and analytical studies of the spin-orbit coupling in heteronuclear alkali-metal dimers AB (A, B = Li, Na, K, Rb) at long ranges. Phys. Rev. A 99, 012507 (2019). [3] W. Jastrzebski, P. Kowalczyk, A. Pashov, J. Szczepkowski. The potential energy barrier of the 2Π1 state in KLi, Spectrochim. Acta A 73, 117–120 (2009). [4] M. Ivanova, A. Stein, A. Pashov, H. Knockel, E. Tiemann. The B1Π and D1Π states of LiRb, J. Chem. Phys. 138, 094315 (2013).