Implementation of an incoherent broadband cavity-enhanced absorption spectroscopy technique in an atmospheric simulation chamber for in situ NO3 monitoring: characterization and validation for kinetic studies

摘要

An incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) technique has been developed for the in situ monitoring of NO3 radicals at the parts per trillion level in the CSA simulation chamber (at LISA). The technique couples an incoherent broadband light source centered at 662nm with a high-finesse optical cavity made of two highly reflecting mirrors. The optical cavity which has an effective length of 82cm allows for up to 3km of effective absorption and a high sensitivity for NO3 detection (up to 6ppt for an integration time of 10s). This technique also allows for NO2 monitoring (up to 9ppb for an integration time of 10s). Here, we present the experimental setup as well as tests for its characterization and validation. The validation tests include an intercomparison with another independent technique (Fourier-transform infrared, FTIR) and the absolute rate determination for the reaction trans-2-butene+NO3, which is already well documented in the literature. The value of (4.13±0.45)×10?13cm3molecule?1s?1 has been found, which is in good agreement with previous determinations. From these experiments, optimal operation conditions are proposed. The technique is now fully operational and can be used to determine rate constants for fast reactions involving complex volatile organic compounds (VOCs; with rate constants up to 10?10cm3molecule?1s?1).