Rotational analyses of two transitions of WS near 13,100 cm−1, and further deperturbation analysis of the [15.30]1 – X 3Σ−0+ transition

Two transitions of tungsten sulfide (WS) near 13,100 cm⁻¹, the (0,0) band of the [13.10]1 – X ³Σ⁻₀₊ transition and the (0,0) band of the [15.30]1 – X ³Σ⁻₁ transition, have been recorded at high resolution using intracavity laser absorption spectroscopy with a Fourier-transform spectrometer used for detection (ILS-FTS). The WS molecules were produced in the plasma discharge formed by applying 0.70–0.80 A of a discharge current from a pulsed DC plasma generator to a tungsten-lined copper hollow cathode. The reaction took place in the presence of Ar (∼70 %), H₂ (∼30 %), and CS₂ (∼0.1 %) gases at a total pressure of approximately 2 torr. Lines for all four abundant isotopologues of WS, ¹⁸²W³²S, ¹⁸³W³²S, ¹⁸⁴W³²S, and ¹⁸⁶W³²S, were measured and a rotational analysis was performed using PGOPHER. A constrained parameters approach was used to maintain expected mass relationships among isotopologues. This analysis increases the number of observed rotational levels from J ∼ 30 to J ∼ 100 for both excited states, allowing an increase in precision of spectroscopic constants. The new analysis of the [15.30]1 – X ³Σ⁻(1) transition enabled the reduced uncertainty in the previously determined value for the splitting of the 0+ and 1 Ω-components of the X ³Σ⁻ ground state. Also presented in this work is an expansion upon our earlier deperturbation analysis involving the [15.30]1 state to include the v′ = 2 vibrational level, which is perturbed by the v′ = 4 vibrational level of the [14.26]0⁺ state.