The limits of signal averaging in atmospheric trace-gas monitoring by tunable diode-laser absorption spectroscopy (TDLAS)


Modern research in atmospheric chemistry requires highly sensitive techniques for the measurement of concentrations of free radicals which determine the rate of photochemical destruction of most atmospheric pollutants. Tunable diode-laser absorption spectroscopy (TDLAS) has already been successfully used for measurements of very low concentrations of stable gases, but further improvement in its sensitivity by signal averaging has been limited by the stability of the instrument. In this paper the concept of the Allan variance is utilized to analyze the stability of an existing frequency-modulated (FM) TDLAS instrument leading to a detection limit for NO2 of 34 pptv at 6 Hz detection bandwidth. The stability of the instrument allows averaging over 60 s. Taking into account the measuring cycle consisting of the determination of the sample spectra and zero air spectra as well as gas exchange in the absorption cell, the detection limit achievable with this particular instrument was 10 pptv within 25 s under laboratory conditions. Possibilities of further improvement of the detection limit are discussed.

This is a preview of subscription content, log in to check access.


  1. 1.

    C.R. Webster, R.T. Menzies, E.D. Hinkley: In: Laser Remote Chemical Analysis, ed. by R.M. Measures (Wiley, New York 1988) p. 163

    Google Scholar 

  2. 2.

    B.J. Finlayson-Pitts, J.N. Pitts, Jr.: Atmospheric Chemistry (Wiley, New York 1986) p. 326

    Google Scholar 

  3. 3.

    R. Grisar, H. Böttner, M. Tacke, G. Restelli (eds.): Monitoring of Gaseous Pollutants by Tunable Diode Lasers (Kluwer, Dordrecht 1992)

    Google Scholar 

  4. 4.

    D.R. Hastie, G.I. Mackay, T. Iguchi, B.A. Ridley, H.I. Schiff: Environ. Sci. Technol. 17, 352A (1983)

  5. 5.

    H.I. Schiff, G.W. Harris, G.I. Mackay: In: The Chemistry of Acid Rain. ed. by R.W. Johnson, G.E. Gordon, W. Calkins, A.Z. Elzerman (Am. Chem. Soc., Washington 1987) p. 274

    Google Scholar 

  6. 6.

    P. Warneck: Chemistry of the Natural Atmosphere (Academic, London 1988)

    Google Scholar 

  7. 7.

    D.R. Crosley, J.M. Hoell (eds.): Future Directions forHxOy detection (NASA Conference Publication No. 2448, Washington 1986)

  8. 8.

    G.C. Bjorklund: Opt. Lett. 5, 15 (1980)

    Google Scholar 

  9. 9.

    P. Werle, F. Slemr, M. Gehrtz, Chr. Bräuchle: Appl. Phys. B 49, 99 (1989)

    Google Scholar 

  10. 10.

    J.A. Silver: Appl. Opt. 31, 707 (1992)

    Google Scholar 

  11. 11.

    D.S. Bomse, A.C. Stanton, J.A. Silver: Appl. Opt. 31, 718 (1992)

    Google Scholar 

  12. 12.

    C.R. Webster: J. Opt. Soc. Am. B 2, 1464 (1985)

    Google Scholar 

  13. 13.

    J.A. Silver, A.C. Stanton: Appl. Opt. 27, 4438 (1988)

    Google Scholar 

  14. 14.

    J. Reid, M. El-Sherbiny, B.K. Garside, E.A. Ballik: Appl. Opt. 19, 3349 (1980)

    Google Scholar 

  15. 15.

    C.B. Carlisle, D.E. Cooper: Opt. Lett. 14, 1306 (1989)

    Google Scholar 

  16. 16.

    F. Slemr, G.W. Harris, D.R. Hastie, G.I. Mackay, H.I. Schiff: J. Geophys. Res. 91, 5371 (1986)

    Google Scholar 

  17. 17.

    G.W. Harris, G.I. Mackay, T. Iguchi, H.I. Schiff: J. Atmos. Environ. 8, 119 (1989)

    Google Scholar 

  18. 18.

    F.C. Fehsenfeld, J.W. Drummond, U.K. Roychowdhury, P.J. Galvin, E.J. Williams, M.P. Buhr, D.D. Parrish, G. Hübler, A.O. Langford, J.G. Calvert, B.A. Ridley, F. Grahek, B.G. Heikes, G.L. Kok, J.D. Shetter, J.G. Walega, C.M. Elsworth, R.B. Norton, D.W. Fahey, P.C. Murphy, C. Hovermale, V.A. Mohnen, K.L. Demerjian, G.I. Mackay, H.I. Schiff: J. Geophys. Res. 95, 3579 (1990)

    Google Scholar 

  19. 19.

    J.K. Taylor: Quality Assurance of Chemical Measurements (Lewis, Chelsea 1988) Chap. 14

    Google Scholar 

  20. 20.

    R.O. Gilbert: Statistical Methods for Environmental Pollution Monitoring (van Nostrand Reinhold, New York 1987) Chap. 15

    Google Scholar 

  21. 21.

    I.N. Bronstein. K.A. Semendjajew: Taschenbuch der Mathematik, 19th edn. (Teubner, Leipzig 1979) Chap. 5.2

    Google Scholar 

  22. 22.

    L. Sachs: Angewandte Statistik, 5th edn. (Springer, Berlin, Heidelberg 1978)

    Google Scholar 

  23. 23.

    J.A. Barnes, A.R. Chi, L.S. Cutler, D.J. Healey, D.B. Leeson, T.E. McGunigal, J.A. Mullen, W.L. Smith, R.L. Sydnor, R.F.C. Vessot, G.M.R. Winkler: IEEE Trans. IM-20, 105 (1971)

    Google Scholar 

  24. 24.

    D.W. Allan: Proc. IEEE 54, 221 (1966)

    Google Scholar 

  25. 25.

    J.A. Barnes: NBS, Washington, DC. Tech. note 375 (1969)

  26. 26.

    W. Demtröder: Laser Spectroscopy (Springer, Berlin, Heidelberg 1982) p. 225

    Google Scholar 

  27. 27.

    R. Schieder, G. Rau, B. Vowinkel: Proc. SPIE 598, 189 (1985)

    Google Scholar 

  28. 28.

    P. Werle, F. Slemr: Appl. Opt. 30, 430 (1991)

    Google Scholar 

  29. 29.

    HITRAN: L.S. Rothman, R.R. Gamache, A. Goldman, L.R. Brown, R.A. Toth, H.M. Picket, R.L. Poynter, J.-M. Flaud, C. Camy-Peyret, A. Barbe, N. Husson, C.P. Rinsland, M.A.H. Smith: Appl. Opt. 26, 4058 (1987)

    Google Scholar 

Download references

Author information



Rights and permissions

Reprints and Permissions

About this article

Cite this article

Werle, P., Mücke, R. & Slemr, F. The limits of signal averaging in atmospheric trace-gas monitoring by tunable diode-laser absorption spectroscopy (TDLAS). Appl. Phys. B 57, 131–139 (1993).

Download citation


  • 07.65