Partial transmission spectra of the mixed gas. The experimental transmittance is compared with the transmission curve calculated from the parameters provided by the HITRAN database, together with the residuals. (a) The full branch lines of the 3v₁ ro-vibration of CO₂ molecule. Part of the absorption of N₂O is contained in the leftmost area. (b) The P14e transition line of the 3v₁ ro-vibration of CO₂ molecule. The circled area contains the weak absorption information of the P24f line of 3v₁+v₂+v₃ to v₂+v₃ ro-vibration.