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arXiv · 2107.13865

Fourier-transform spectroscopy and relativistic electronic structure calculation on the $c^3\Sigma^+$ state of KCs

Artis Kruzins·Valts Krumins·Maris Tamanis·Ruvin Ferber·Alexander V. Oleynichenko·Andrei Zaitsevskii·Elena A. Pazyuk·Andrey V. Stolyarov
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Abstract

The Ti:Saphire laser operated within 13800 - 11800 cm$^{-1}$ range was used to excite the $c^3\Sigma^+$ state of KCs molecule directly from the ground $X^1\Sigma^+$ state. The laser-induced fluorescence (LIF) spectra of the $c^3\Sigma^+ \rightarrow a^3\Sigma^+$ transition were recorded with Fourier-transform spectrometer within 8000 to 10000 cm$^{-1}$ range. Overall 673 rovibronic term values belonging to both $e/f$-components of the $c^3\Sigma^+(\Omega=1^{\pm})$ state of $^{39}$KCs, covering vibrational levels from $v$ = 0 to about 45, and rotational levels $J\in [11,149]$ were determined with the accuracy of about 0.01 cm$^{-1}$; among them 7 values for $^{41}$KCs. The experimental term values with $v\in [0,22]$ were involved in a direct point-wise potential reconstruction for the $c^3\Sigma^+(\Omega=1^{\pm})$ state, which takes into account the $\Omega$-doubling effect caused by the spin-rotational interaction with the nearby $c^3\Sigma^+(\Omega=0^-)$ state. The analysis and interpretation were facilitated by the fully-relativistic coupled cluster calculation of the potential energy curves for the $B^1\Pi$, $c^3\Sigma^+$, and $b^3\Pi$ states, as well as of spin-forbidden $c-X$ and spin-allowed $c-a$ transition dipole moments; radiative lifetimes and vibronic branching ratios were calculated. A comparison of relative intensity distributions measured in vibrational $c-a$ LIF progressions with their theoretical counterparts unambiguously confirms the vibrational assignment suggested in [\emph{J. Szczepkovski, et. al.}, JQSRT, \textbf{204}, 133-137 (2018)].

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Artis Kruzins, Valts Krumins, Maris Tamanis, Ruvin Ferber, Alexander V. Oleynichenko, Andrei Zaitsevskii, Elena A. Pazyuk, Andrey V. Stolyarov. 2021-07-29. Fourier-transform spectroscopy and relativistic electronic structure calculation on the $c^3\Sigma^+$ state of KCs. https://doi.org/10.1016/j.jqsrt.2021.107902

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