Fig. 1. CO₂ absorption line ranging from 6 313 cm⁻¹ to 6 410 cm⁻¹

Fig. 2. Selected CO₂ absorption lines

Fig. 3. Flow chart of Levenberg-Marquardt algorithm

Fig. 4. Schematic diagram of experimental setup of wavelength scanning method

Fig. 5. Schematic diagram of test system

Fig. 6. Absorption signal

Fig. 7. Signal processing process

Fig. 8. Relationship of CO₂ absorption values and concentration

Fig. 9. Fitting residuals