The rotational-vibrational spectra of HNCS and DNCS : An analysis of the high resolution spectra

Ro-vibrational spectra of HNCS and DNCS have been obtained in the spectral range 300–4000 cm⁻¹ with a practical resolution limit of 0.06 cm⁻¹ in the region 350–1200 cm⁻¹ and 0.15 cm⁻¹ in the region 1200–4000 cm⁻¹. The observed fine structure permitted definitive assignments for some of the ^PQ_K, ^QQ_K, and ^RQ_K branches in both molecules, and yielded sets of rotational constants in substantial agreement with those obtained from recent microwave and far-infrared studies. Precise estimates of the band origins have been obtained and there is evidence of second-order Coriolis coupling between the three bending modes in each molecule. The isolation of the out-of-plane bending modes has lead to a re-assignment of ν₃, ν₄, ν₅, and ν₆ for each molecule. The band origins, uncorrected for Coriolis interaction, are for HNCS and DNCS, respectively. v₁:3538.6 ±0.3, 2644.5±0.5cm⁻¹;v₂:1989.0 ±0.3, 1944.3±0.5cm⁻¹;v₃:857.0 ±0.6, 851.0±0.1cm⁻¹;v₄:615.0 ±0.5, 549.1±0.2cm⁻¹;v₅:469.2 ±0.1, 365.8 ±0.2cm⁻¹;v₆:539.2 ±0.5, 481.0±0.1cm⁻¹;