Nitrogen Oxide Cavity Ring Down Spectrometer (NOxCaRD)

Cavity ring down spectroscopy (CRDS) is a high sensitivity absorption technique that exploits an optical cavity, in this case, two high reflectivity mirrors aligned parallel to one another, to achieve optical paths up to 100 km in a 50 - 100 cm cell.  Diode lasers are readily available at 405 nm, near the maximum in the absorption spectrum of nitrogen dioxide, NO₂, enabling measurement with a precision to 20 parts per trillion by volume (pptv) at 1 second time resolution with an accuracy better than 5%.  Quantitative inlet conversions provide simultaneous measurements of nitric oxide (NO), ozone (O₃) and total reactive nitrogen (NO_y).

The Nitrogen Oxide Cavity Ring Down Spectrometer (NOxCaRD) is a four-channel instrument for NO, NO₂, NO_y, and O₃.  It is well-suited for light aircraft and mobile laboratories and has participated in the recent FAST-LVOS and UWFPS field studies, among others.

References

Brown, S.S., H.J. An, M. Lee, J.H. Park, S.D. Lee, D.L. Fibiger, E.E. McDuffie, W.P. Dubé, N.L. Wagner, and K.E. Min, Cavity Enhanced Spectroscopy for Measurement of Nitrogen Oxides in the Anthropocene: Results from the Seoul Tower during MAPS 2015. Faraday Discussions, 2017. 200: p. 529-557. https://pubs.rsc.org/en/content/articlelanding/2017/fd/c7fd00001d#!divAbstract

Wild, R.J., P.M. Edwards, W.P. Dubé, K. Baumann, E.S. Edgerton, P.K. Quinn, J.M. Roberts, A.W. Rollins, P.R. Veres, C. Warneke, E.J. Williams, B. Yuan, and S.S. Brown, A Measurement of Total Reactive Nitrogen, NO_y, together with NO₂, NO and O₃ via Cavity Ring-Down Spectroscopy. Environ. Sci. Technol., 2014. 48: p. 9609-9615. http://pubs.acs.org/doi/abs/10.1021/es501896w 

Washenfelder, R.A., W.P. Dubé, N.L. Wagner, and S.S. Brown, Measurement of atmospheric ozone by cavity ring-down spectroscopy. Environ. Sci. Technol., 2011. 45: p. 2938-2944. https://pubs.acs.org/doi/abs/10.1021/es103340u

Fuchs, H., W.P. Dubé, B.M. Lerner, N.L. Wagner, E.J. Williams, and S.S. Brown, A sensitive and versatile detector for atmospheric NO₂ and NO_x based on blue diode laser cavity ring-down spectroscopy. Environ. Sci. Technol., 2009. 43: p. 7831-7836. https://pubs.acs.org/doi/abs/10.1021/es902067h