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Prototype for In Situ Detection of Atmospheric NO3 and N2O5 via Laser-Induced...

Wood, E. C., P. J. Wooldridge, J. H. Freese, T. Albrecht, and R. C. Cohen (2003), Prototype for In Situ Detection of Atmospheric NO3 and N2O5 via Laser-Induced Fluorescence, Environ. Sci. Technol., 37, 5732-5738, doi:10.1021/es034507w.

We describe a prototype designed for in situ detection of the nitrate radical (NO3) by laser-induced fluorescence (LIF) and of N2O5 by thermal dissociation followed by LIF detection of NO3. An inexpensive 36 mW continuous wave multi-mode diode laser at 662 nm is used to excite NO3 iñ the B 2E ′(0000) r X 2A2(0000) band. Fluorescence is collected from 700 to 750 nm. The prototype has a sensitivity to NO3 of 76 ppt for a 60 s integration with an accuracy of 8%. Although this sensitivity is adequate for studies of N2O5 in many environments, it is much less sensitive (about 300 times) than expected based on a comparison of previously measured photophysical properties of NO2 and NO3. This implies much stronger nonradiative coupling of electronic states in NO3 than in NO2.

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