Doppler-limited and atmospheric spectra of the 4-μm ν1 + ν3 combination band of SO2

Abstract The combination vibration-rotation ν 1 + ν 3 band of SO 2 has been recorded under Doppler-limited and atmospheric conditions with 3 × 10 −4 cm −1 instrumental resolution using a difference-frequency laser. The spectra are compared to recent theories based on rotational constants from microwave data.