Experimental Determination of the Vibrational Constants of FeS(X⁵△) by Dispersed Fluorescence Spectroscopy

Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X⁵△ electronic state were obtained by directly mapping the ground-state vibrational levels up to v″=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS(X⁵△) (518±5 cm-1) agrees well with that reported in a recent PES measurement (520±30 cm-1) J. Phys. Chem. A 107, 2821 (2003) which is the only one prior experimental vibrational frequency value for the ⁵△ state of FeS. Careful comparisons of our experimental results and those documented in the literature (mainly from theoretical predictions) suggest that the ground state of FeS is ⁵△ state.