First high-resolution analysis of the ν₁, ν₃ and ν₁ + ν₃ bands of sulphur dioxide ³³S¹⁶O₂

High-resolution spectra of ³³S¹⁶O₂ have been recorded for the first time in the 8 and 4 µm spectral regions.The ν₁, ν₃ and ν₁ + ν₃ bands of the ³³S¹⁶O₂ have been analysed up to very high quantum numbers.Accurate ro-vibrational upper states constants have been determined. High-resolution spectra of ³³S¹⁶O₂ have been recorded for the first time in the 8 and 4 µm spectral regions. The ν₁, ν₃ and ν₁ + ν₃ bands of the ³³S¹⁶O₂ have been analysed up to very high quantum numbers. Accurate ro-vibrational upper states constants have been determined. Fourier transform spectra of sulphur dioxide ³³S¹⁶O₂ have been recorded in the 8.0 and 4.0 µm spectral regions at a resolution of 0.0015 cm⁻¹ using a Bruker IFS 125HR spectrometer leading to the observation of the ν₁, ν₃ and ν₁ + ν₃ vibrational bands of the ³³S¹⁶O₂ molecule. The corresponding upper state ro-vibrational levels were fit using a Hamiltonian matrix taking into account a Coriolis Δ<i>K_a </i> = 3 resonance between the ro-vibrational levels of the 1¹ and 3¹ vibrational states and a Watson-type Hamiltonian for the ro-vibrational levels of the 1¹ 3¹ vibrational state. In this way it was possible to reproduce the upper state ro-vibrational levels to within the experimental uncertainty; i.e. ∼0.20 × 10⁻³ cm⁻¹. Very accurate rotational and centrifugal distortion constants were derived from the fit together with the following band centres: ν₀ (ν₁) = 1147.979535(60) cm⁻¹, ν₀ (ν₃) = 1353.335912(60) cm⁻¹ and ν₀ (ν₁ + ν₃) = 2487.493732(30) cm⁻¹.