Fig. 1. Experimental setup of the high precision cavity system (a), schematic layouts of reference mode (b) and sampling mode (c) of its flow system

Fig. 2. (a) Absorption cross sections of O₃, C₆H₆, C₇H₈, C₈H₁₀ in the 245~285 nm band; (b) LED spectra (red curve, 20 ℃, 350 mA) and reflectivity of high reflective mirrors (black curve), where the LED (λ = 266 nm, FWHM = 11 nm) spectra were measured using a spectrometer, and the high reflectivity curve of cavity mirrors is 100×(R-0.99), herein R is the reflectivity of high reflecting cavity mirrors in a certain wavelength range

Fig. 3. Relationship of DUV-LED radiant light intensity with driving current and temperature. (a) LED radiation intensity at different currents when the set temperature is unchanged; (b) LED radiation intensity at different temperatures when the set driving current is unchanged; (c) Effect of the change of driving current on the center wavelength of LED and relative peak intensity; (d) Effect of the change of temperature on the center wavelength of LED and relative peak intensity

Fig. 4. Calibrating the system with known molecular concentration of ozone to obtain the effective path length L_eff of the optical cavity

Fig. 5. System performance test. (a) Concentration time series; (b) Concentration histogram; (c) Allan deviation plot of ozone free air measurement, showing the dependence of 1σ accuracy on integration time

Fig. 6. measurement comparison between the self-developed high-precision cavity system and the commercial ozone analyzer.(a) O₃ concentration time series of the two systems; (b) Correlation plot of O₃ concentration time series of the two systems