Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 3 2008 10.5194/acpd-8-10665-2008 http://www.atmos-chem-phys-discuss.net/8/10665/2008/ http://www.atmos-chem-phys-discuss.net/8/10665/2008/acpd-8-10665-2008.html http://www.atmos-chem-phys-discuss.net/8/10665/2008/acpd-8-10665-2008.pdf 10665 10695 2008-06-04 Using a high finesse optical resonator to provide a long light path for differential optical absorption spectroscopy: CE-DOAS J. Meinen jan.meinen@imk.fzk.de J. Thieser U. Platt T. Leisner Institute for Meteorology and Climate Research, Aerosols and Heterogeneous Chemistry in the Atmosphere (IMK-AAF), Forschungszentrum Karlsruhe GmbH, Germany Institut for Environmental Physics (IUP), Atmosphere and Remote Sensing, Ruprecht-Karls-Universität Heidelberg, Germany Cavity enhanced methods in absorption spectroscopy have seen a considerable increase in popularity during the past decade. Especially Cavity Enhanced Absorption Spectroscopy (CEAS) established itself in atmospheric trace gas detection by providing tens of kilometers of effective light path length using a cavity as short as 1 m. In this paper we report on the construction and testing of a compact and power efficient light emitting diode based broadband Cavity Enhanced Differential Optical Absorption Spectrometer (CE-DOAS) for in situ field observation of atmospheric NO₃. This device combines the small size of the cavity with the enormous advantages of the DOAS approach in terms of sensitivity and specificity. In particular, no selective removal of the analyte (here NO₃) is necessary, thus the CE-DOAS technique can – in principle – measure any gas detectable by DOAS. We will discuss the advantages of using a light emitting diode (LED) as light source particularly the precautions which have to be satisfied for the use of LEDs. The instrument was tested in the lab by detecting NO₃ in a mixture of NO₂ and O₃ in air. It was then compared to other trace gas detection techniques in an intercomparison campaign in the atmosphere simulation chamber SAPHIR at NO₃ concentrations as low as 6.3 ppt. Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., and Troe, J.: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume I – gas phase reactions of Ox, Hox, Nox and Sox species, 4, 1461–1738, 2004. Ball, S. M., Povey, I. M., Norton, E. G., and Jones R. L.: Broadband cavity ringdown spectroscopy of the NO₃ radical, Chem. Phys. Lett., 342, 113–120, 2001. Ball, S. M. and Jones, R. L.: Broad-Band Cavity Ring-Down Spectrscopy, Chem. Rev., 103, 5239–5262, 2003. Ball, S. M., Langridge, J. M., and Jones, R. L.: Broadband cavity enhanced absorption spectroscopy using light emitting diodes, Chem. Phys. Lett., 398, 68–74, 2004. Brown, S. S.: Absorption Spectroscopy in High-Finesse Cavities for Atmospheric Studies, Chem. Rev., 103, 5219–5238, 2003. Dorn, H.-P., Brandenburger, U., Brauers, T., and Hausmann, M.: A new in-situ laser long-path absorption instrument for the measurement tropospheric OH radicals., J. Atmos. Sci. 52, 3373–3380, 1995. Engeln, R., Berden, G., Peeters, R., and Meijer, G.: Cavity enhanced absorption and cavity enhanced magnetic rotation spectroscopy, Rev. Sci. Instrum., 69, 3763–3769, 1998. Fiedler, S. E., Hese, A. and Ruth, A. A.: Incoherent broad-band cavity-enhanced absorption spectroscopy, Chem. Phys. Lett., 371, 284–294, 2003. Fiedler, S. E. and Hese, A.: Influence of the cavity parameters on the output intensity in incoherent broadband cavity-enhanced absorption spectroscopy, Rev. Sci. Instr., 78, 0731041–0731047, 2007. Hamers, E., Schram, D. and Engeln, R.: Fourier transform phase shift cavity ring down spectroscopy, Chem. Phys. Lett., 265, 237-243, 2002. Herriot, D. R. and Schulte, H. J.: Folded Optical Delay Lines, Appl. Optics, 4, 883–889, 1965. Hönninger, G., Friedeburg, C. V., and Platt, U.: Multi axis differential optical absorption spectroscopy (MAX-DOAS), Atmos. Chem. Phys., 4, 231–254, 2004. Kern, C., Trick, S., Rippel, B., and Platt, U.: Applicability of light-emitting diodes as light sources for active differential optical absorption spectroscopy measurements, Appl. Optics, 45, 2077–2088, 2006. Kraus, S. G..: DOASIS, A Framework Design for DOAS., Doctoral Thesis, University of Heidelberg, Germany, see also: http://www.iup.uni-heidelberg.de/bugtracker/projects/doasis/, 2006. Langridge, J. M., Stephen, M. B., and Jones, R. L.: A compact broadband cavity enhanced absorption spectrometer for detection of atmospheric NO₂ using light emitting diodes, Analyst, 131, 916–922, 2006. O'Keefe, A., Scherer, J. J., and Paul, J. B.: cw Integrated cavity output spectroscopy, Chem. Phys. Lett., 307, 343–349, 1999. Paul, J. B., Lapson, L. and Anderson, J. G.: Ultrasensitive absorption spectroscopy with a high-finesse optical cavity and off-axis alignment, Appl. Optics, 40, 4904–4910, 2001. Platt, U. and Perner, D.: Direct measurements of atmospheric CH₂O, HNO₂, O₃, NO₂, SO₂ by differential optical absorption in the near UV, J. Geophys. Res., 85, 7453–7458, 1980. Ruth, A. A., Orphal, J., and Fiedler, S. E.: Fourier-transform cavity-enhanced absorption spectroscopy using an incoherent broadband light source, Appl. Optics, 46, 3611–3616, 2007. Simpson, W. R.: Continuous wave cavity ring-down spectroscopy applied to in situ detection of dinitrogen pentoxide (N2O5), Rev. Sci. Instr., 74, 1–11, 2003. Sneep, M. and Ubachs, W.: Direct measurement of the Rayleigh scattering cross section in various gases, J. Quant. Spectrosc. Ra., 92, 293–310, 2005. Venables, D. S., Gherman, T., Orphal, J., Wenger, J. C., and Ruth, A. A.: High Sensitive in Situ Monitoring of NO3 in an Atmospheric Simulation Chamber Using Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy, Environ. Sci. Technol., 40, 6758–6763, 2006. White, J. U.: Long optical paths of large aperture, J. Opt. Soc. Am., 32, 285–288, 1942. Yokelson, R. J., Burkholder, J. B., Fox, R. W., Talukdar, R. K., and Ravishankara, A. R.: Temperature Dependence of the NO₃ Absorption Spectrum, J. Phys. Chem., 98, 13144–13150, 1994.