V. A. Alekseev, “Ab initio study of the interaction potentials of CF$_4$, CH$_4$, SiF$_4$ and SiH$_4$ molecules with the Rb atom in the ground and electronically excited states”, Optics and Spectroscopy, 2022, Volume 130, Issue 9,Pages 1343

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Spectroscopy and physics of atoms and molecules

Ab initio study of the interaction potentials of CF$_4$, CH$_4$, SiF$_4$ and SiH$_4$ molecules with the Rb atom in the ground and electronically excited states

V. A. Alekseev^ab

^a I. V. Grebenshchikov Institute of Silicate Chemistry of the Russian Academy of Sciences, St. Petersburg
^b St. Petersburg National Research University of Information Technologies, Mechanics and Optics

Abstract: The potentials of the electronic states of RbXY$_4$ molecules, RbXY$_4$, XY$_4$ = CF$_4$, CH$_4$, SiF$_4$ and SiH$_4$, correlating with the ground $5s$ $^2S_{1/2}$ and excited $5p$ $^2P_{1/2,3/2}$ states of the Rb atom are studied using the methods of ab initio quantum chemistry. The calculations are performed by the SCF method of the full active space of orbitals, taking into account dynamic electronic correlations and spin-orbital interaction. It is established that the character of the interaction in the $A$ and $A'$ states, correlating respectively with the lower and upper states of the Rb ($5p$ $^2P_{1/2,3/2}$) doublet and corresponding to the perpendicular orientation of the Rb $p$-orbital relative to the Rb–X axis, differ significantly (attraction or repulsion) for different XY$_4$ molecules, which is explained by the difference in the charge distribution in the XY$_4$ molecules. In order to evaluate the accuracy of the calculation results for RbXY$_4$ molecules, similar calculations are performed for the diatomic RbAr molecule using different basis sets. It is found that, as compared with the $A$ and $A'$ states, the potential of the repulsive B state, which correlates with the upper state of the doublet and corresponds to the orientation of the Rb $p$-orbital along the Rb–X axis, is significantly more sensitive to the size of the basis set which is due to the accuracy of accounting for the configuration interaction with states that correlate with the Rb($6s$ $^2S_{1/2}$) and Rb ($4d$ $^2D_{3/2,5/2}$) states and other states of the Rb atom lying above Rb ($5p$ $^2P_{1/2,3/2}$).

Keywords: alkali metals, excited states, carbon tetrafluoride, quantum chemistry, ab initio calculations.

Received: 29.03.2022
Revised: 10.07.2022
Accepted: 11.07.2022

DOI: 10.21883/OS.2022.09.53293.3458-22