基于腔衰荡技术搭建了一套热解双腔式腔衰荡光谱(TD-CRDS)探测系统用于环境大气二氧化氮(NO2)和有机硝酸酯(Organic Nitrate, ON)的快速同步测量。二氧化氮是通过其对406 nm处激光的吸收来直接进行测量的,而有机硝酸酯是通过将其在450 ℃高温下热解为NO2进行间接测量的,在该温度下,ON的转化效率可达到99%。使用中心波长为406.02 nm的激光器,经NO2高分辨吸收截面与激光光谱卷积获得NO2的有效吸收截面为5.74×10 -19 cm 2·molecule -1;对加热装置进行稳定性测试,确定最佳流速为1 L/min;NO2腔与ON腔同步测量环境大气中的NO2具有非常好的一致性,相关性系数R2为0.99。经优化,本探测系统的探测限可达2.42×10 9 molecule·cm -3 (标准差为3σ,时间分辨率为1 s)。将TD-CRDS系统与长光程差分吸收光谱(LP-DOAS)测量的NO2进行对比,两者一致性较好,R2为0.93,说明系统测量具有较好的准确性。将该系统应用于外场实验中,获得了NO2和ON的浓度序列。

In this study, a two-channel thermal dissociation cavity ring-down spectroscopy (TD-CRDS) system based on cavity ring-down spectroscopy technology was established for the rapid and simultaneous measurement of ambient nitrogen dioxide (NO₂) and organic nitrates (ON). NO₂ was directly measured by its absorption at 406 nm, while ON was indirectly measured by the NO₂ product of its thermal decomposition at 450 ℃. The ON conversion efficiency reached 99% at this temperature. The effective absorption cross-section of NO₂ was obtained by the convolution of the high-resolution absorption cross-section of NO₂ using a laser with a central wavelength of 406.02 nm. The laser spectrum was 5.74×10 ^-19 cm ²·molecule ^-1. A stability test of the heating device revealed an optimal flow rate of 1 L/min. The simultaneous measurement of the ambient NO₂ by the NO₂ and ON cavities exhibited good consistency, with the correlation coefficient R²=0.99. After optimization, the detection limit of the system reached up to 2.42×10 ⁹ molecule·cm ^-3 (standard deviation: 3σ; temporal resolution: 1 s). Comparing the TD-CRDS system with the long-path differential optical absorption spectroscopy (LP-DOAS) in terms of NO₂ measurement, good consistency was obtained (R²=0.93), indicating that the system has high measurement accuracy. The TD-CRDS system was applied to field observation, and the time series of NO₂ and ON concentration were obtained.