Fig. 1. N₂O₅ synthesis system

Fig. 2. The absorption cross-sections of NO₂ and O₃ at room temperature

Fig. 3. N₂O₅ cavity ring-down spectroscopy system

Fig. 4. Damping signal curve and damping time fitting

Fig. 5. Decay signal of N₂O₅-CRDS detection system (a) and Allan variance for NO₃ radical measurement (b)

Fig. 6. The original data of N₂O₅ in high-concentration state (a) and the autocorrelation function (b) and partial autocorrelation function (c) plots of the concentration-time series

Fig. 7. The changes of NO₃ and N₂O₅ in the simulated synthesis gas over the time from the outlet of the synthesis tube to leaving the decay tube

Fig. 8. The concentration changes of N₂O₅ source through PFA tubing of different lengths

Fig. 9. The concentration changes of N₂O₅ source passing through new and used filter membranes, as well as without a filter membrane

Fig. 10. Structural diagram for measuring N₂O₅ loss on the wall of PFA tude with outer diameter of 12.7 mm

Fig. 11. Mass concentration changes of N₂O₅ source after passing through heated PFA tubes of different lengths