Observation and analysis of a new [14.26]0+ – X3Σ–0+ transition of WS, observed using intracavity laser spectroscopy with Fourier-transform detection

Abstract

The (1,0), (0,1), and (1,2) bands of a new [14.26]0+ – X3Σ–0+ transition of WS are described. The WS molecules were produced in the plasma discharge formed when either a 0.15 A DC plasma current or a 0.80 A RF-pulsed DC plasma current was applied to a W-lined Cu hollow cathode in an atmosphere that was 0.1%CS2, ~30% H2 and ~70% Ar at a total pressure of 1–2 torr. The hollow cathode was located in the resonator cavity of either a Ti:Sapphire or dye laser (with DCM laser dye), causing molecular absorption to be superimposed upon the tunable broadband profile of the laser. This profile was detected using a Bruker IFS 125 M spectrometer with an instrument resolution set to 0.01 cm−1. Effective pathlengths for the ILS-FTS measurements were 170 m (Δv = +1) and 535 m (Δv = –1). The ILS-FTS spectra were rotationally analyzed using PGOPHER. Transitions of 182W32S, 183W32S, 184W32S, and 186W32S were identified for all three bands, and a mass-independent Dunham model was built in PGOPHER to fit the X3Σ–0+ ground state of WS. Experimental line positions from the laser induced fluorescence (LIF) spectrum of WS [Tsang et al., J. Mol. Spectrosc.359 (2019) 31] and our analysis of the (1,0) band of the [13.10]1–X3Σ–0+ transition [Harms et al., J. Mol. Spectrosc.372 (2020) 111349] were included in the PGOPHER fit. A correlation diagram between the experimentally observed states and those predicted ab initio [Tsang et al.] is used to shed light on the complex electronic spectrum of WS.