Fig. 1. Flowchart of PSO peak correction

Fig. 2. Schematic diagram of PSO iteration process

Fig. 3. Schematic diagram of CO₂ measurement device using VIPA spectrometer

Fig. 4. Spectral measurement images and spectral calibration results of polynomial method. (a) Pure N₂ spectral image; (b) pure CO₂ spectral image; (c) measured spectrum, theoretical absorption spectrum, and residual of pure CO₂ in frequency axis calibrated by cubic polynomial; (d) local fitting plot and residual from 6988.25 cm^-1 to 6988.70 cm^-1

Fig. 5. Particle motion diagrams and corresponding spectral fitting diagrams under different iterations within 6988.25‒6988.70 cm^-1. (a) Position of particle swarm at first iteration; (b) fitting plot and residual of global optimal position at first iteration; (c) position of particle swarm at 15th iteration; (d) fitting plot and residual of global optimal position at 15th iteration; (e) position of particle swarm at 30th iteration; (f) fitting plot and residual of global optimal position at 30th iteration

Fig. 6. Change process of fitness value

Fig. 7. Measured spectrum, theoretical absorption spectrum, and residual of pure CO₂ after PSO peak correction

Fig. 8. Results of cubic polynomial fitting frequency axis solution and solution after particle swarm correction at 30% to 60% volume fraction