Fourier transform spectroscopy and direct potential fit of a shelflike state: Application to E(4)(1)Sigma(+) KCs

作者：Busevica L^*; Klincare I; Nikolayeva O; Tamanis M; Ferber R; Meshkov V V; Pazyuk E A; Stolyarov A V

来源：Journal of Chemical Physics, 2011, 134(10): 104307.

DOI：10.1063/1.3561318

The paper presents high-resolution experimental study and a direct potential construction of a shelflike state E(4)(1)Sigma(+) of the KCs molecule converging to K(4(2)S) + Cs(5(2)D) atomic limit; such data are of interest for selecting optical paths for producing and monitoring cold polar diatomics. The collisionally enhanced laser induced fluorescence (LIF) spectra corresponding to both spin-allowed E(4)(1)Sigma(+) -> X(1)(1)Sigma(+) and spin-forbidden E(4)(1)Sigma(+) -> a(1)(3)Sigma(+) transitions of KCs were recorded in visible region by Fourier transform spectrometer with resolution of 0.03 cm(-1). Overall about 1650 rovibronic term values of the E(4)(1)Sigma(+) state of (KCs)-K-39-Cs-133 and (KCs)-K-41-Cs-133 isotopologues nonuniformly covering the energy range [16987, 18445] cm(-1) above the minimum of the ground X-state were determined with the uncertainty of 0.01 cm(-1). Experimental data field is limited by vibrational levels v' is an element of [2, 74] with rotational quantum numbers J' is an element of [1, 188]. The closed analytical form for potential energy curve (PEC) based on Chebyshev polynomial expansion (CPE) was implemented to a direct potential fit (DPF) of the experimental term values of the most abundant (KCs)-K-39-Cs-133 isotopologue. Besides analyticity, regularity, correct long-range behavior, and nice convergence properties, the CPE form demonstrated optimal balance on flexibility and constraint for the DPF of a shelflike state aggravated by a limited data set. The mass-invariant properties of the CPE PEC were tested by the prediction of rovibronic term values of the (KCs)-K-41-Cs-133 isotopomer which coincided with their experimental counterparts with standard deviation of 0.0048 cm(-1). The CPE modeling is compared with the highly flexible pointwise inverted perturbation approach model, as well as with conventional Dunham analysis of restricted data set v' <= 50. Reliability of the empirical PEC is additionally confirmed by good agreement between the calculated and experimental relative intensity distributions in the long E(v') -> X(v '') LIF progressions.

• 出版日期2011-3-14