6533b838fe1ef96bd12a4448

RESEARCH PRODUCT

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

subject

description

The Ti:Saphire laser operated within 13800 - 11800 cm$^{-1}$ range was used to excite the $c^3��^+$ state of KCs molecule directly from the ground $X^1��^+$ state. The laser-induced fluorescence (LIF) spectra of the $c^3��^+ \rightarrow a^3��^+$ 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 $c^3��^+(��=1^{\pm})$ 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 $c^3��^+(��=1^{\pm})$ state, which takes into account the $��$-doubling effect caused by the spin-rotational interaction with the nearby $c^3��^+(��=0^-)$ state. The analysis and interpretation were facilitated by the fully-relativistic coupled cluster calculation of the potential energy curves for the $B^1��$, $c^3��^+$, and $b^3��$ 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)].