Electronic transitions of tungsten monosulfide

Abstract

Electronic transition spectrum of the tungsten monosulfide (WS) molecule in the near infrared region between 725 nm and 885 nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The WS molecule was produced by reacting laser - ablated tungsten atoms with 1% CS2 seeded in argon. Fourteen vibrational bands with resolved rotational structure have been recorded and analyzed, which were organized into six electronic transition systems. Least-squares fit of the measured line positions yielded molecular constants for the electronic states observed. The ground state has been identified to be the X3Σ−(0+) state with bond length, ro, and vibrational frequency, ΔG1/2, determined to be 2.0676 Å and 556.7 cm−1 respectively. Molecular constants and potential energy curves of low-lying Λ-S states and Ω sub-states of the WS molecule have been calculated at the MRCISD + Q level of theory with spin-orbit coupling. Calculated molecular properties of the ground and low-lying electronic states are generally in good agreement with experimental determinations. This work represents the first experimental investigation of the electronic transition spectrum of the WS molecule.