Abstract

The photoacoustic determination of the ammonia concentration in atmospheric air by absorption of CO2 laser radiation at 9.22 μm is influenced by the presence of H2O and CO2. Kinetic cooling due to the coupling of excited CO2 and N2 levels causes important changes in phase and amplitude of the photoacoustic signal. Theoretical background is presented to deduce the correct NH3 concentration from the signal. The experimental setup used to perform field measurements is described. Adhesion of NH3 to the walls of the resonant photoacoustic cell was investigated. Temperature effects are treated. Field data of NH3 and H2O concentrations are presented.

© 1990 Optical Society of America

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  1. J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
    [CrossRef]
  2. S. M. Beck, “Cell Coatings to Minimize Sample (NH3 and N2H4) Adsorption for Low Level Photoacoustic Detection,” Appl. Opt. 24, 1761–1763 (1985).
    [CrossRef] [PubMed]
  3. A. D. Wood, M. Camac, E. T. Gerry, “Effects of 10.6 μ Laser Induced Air Chemistry on the Atmospheric Refractive Index,” Appl. Opt. 10, 1877–1884 (1971).
    [CrossRef] [PubMed]
  4. R. J. Brewer, C. W. Bruce, “Photoacoustic Spectroscopy of NH3 at the 9-μm and 10-μm 12C16O2 Laser Wavelengths,” Appl. Opt. 17, 3746–3749 (1978).
    [CrossRef] [PubMed]
  5. P. L. Meyer, M. W. Sigrist, “Air-Pollution Monitoring With Mobile CO2-Laser Photo-Acoustic System,” Ph.D. Thesis 8651 ETH Zurich (of P. L. Meyer) (1988).
  6. R. A. Rooth, A. J. L. Verhage, L. W. Wouters, L. van den Beld, “On the Photo-Acoustic Measurement of Ammonia in the Atmosphere,” in Proceedings, Fourth International Conference on Infrared Physics (ETH, Zurich, 1988), pp. 593–595.
  7. J. Hinderling, M. W. Sigrist, F. K. Kneubuhl, “Field and Laboratory Experiments on the 8 to 14 μm Spectral Window of the Terrestrial Atmosphere,” Int. J. Infrared Phys. Millimeter Waves 7, 683–713 (1986).
    [CrossRef]
  8. L. S. Rothman et al., “The HITRAN Data Base: 1986 Edition,” Appl. Opt. 26, 4058–4097 (1987).
    [CrossRef] [PubMed]
  9. F. E. Hovis, C. B. Moore, “Vibrational Relaxation of NH3 (ν2),” J. Chem. Phys. 69, 4947–4950 (1978).
    [CrossRef]
  10. F. E. Hovis, C. M. Moore, “Temperature Dependence of Vibrational Energy Transfer in NH3 and H218O,” J. Chem. Phys. 72, 2397–2402 (1980).
    [CrossRef]
  11. V. P. Zharov, V. S. Letokhov, Laser Opto-Acoustic Spectroscopy (Springer-Verlag, New York, 1986).
  12. S. H. Bauer, J. F. Caballero, R. Curtis, J. R. Wiesenfeld, “Vibrational Relaxation Rates of CO2 (001) with Various Collision Partners for T <300 K,” J. Chem. Phys. 91, 1778–1785 (1987).
    [CrossRef]
  13. A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
    [CrossRef]
  14. A. J. Zuckerwar, W. A. Griffin, “Effect of Water Vapour on Sound Absorption in Nitrogen at Low Frequency/Pressure Ratios,” J. Acoust. Soc. Am. 69, 150–154 (1981).
    [CrossRef]
  15. R. L. Taylor, S. Bitterman, Survey of Vibrational Relaxation Data for Processes Important in the CO2-N2 Laser System,” Rev. Mod. Phys. 41, 26–47 (1969).
    [CrossRef]
  16. A. Rosencwaig, Photoacoustics and Photoacoustic Spectroscopy (Wiley, New York, 1980).
  17. E. Kritchman, S. Shtrikman, M. Slatkine, “Resonant Optoacoustic Cells for Trace Gas Analysis,” J. Opt. Soc. Am. 68, 1257–1271 (1978).
    [CrossRef]
  18. F. Harren, “The Photoacoustic Effect, Refined and Applied to Biological Problems,” Thesis, Catholic University of Nijmegen, The Netherlands (1988).
  19. P. M. Morse, K. U. Ingard, Theoretical Acoustics (Princeton U.P., 1986).
  20. B. D. Kay, T. D. Raymond, M. E. Coltrin, “Observation of Direct Multiquantum Vibrational Excitation in Gas-Surface Scattering: NH3 on Au(111),” Phys. Rev. Lett. 59, 2792–2794 (1990).
    [CrossRef]
  21. M. J. Kavaya, J. S. Margolis, M. S. Shumate, “Optoacoustic Detection Using Stark Modulation,” Appl. Opt. 18, 2602–2606 (1979).
    [CrossRef] [PubMed]

1990 (1)

B. D. Kay, T. D. Raymond, M. E. Coltrin, “Observation of Direct Multiquantum Vibrational Excitation in Gas-Surface Scattering: NH3 on Au(111),” Phys. Rev. Lett. 59, 2792–2794 (1990).
[CrossRef]

1988 (1)

J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
[CrossRef]

1987 (2)

S. H. Bauer, J. F. Caballero, R. Curtis, J. R. Wiesenfeld, “Vibrational Relaxation Rates of CO2 (001) with Various Collision Partners for T <300 K,” J. Chem. Phys. 91, 1778–1785 (1987).
[CrossRef]

L. S. Rothman et al., “The HITRAN Data Base: 1986 Edition,” Appl. Opt. 26, 4058–4097 (1987).
[CrossRef] [PubMed]

1986 (1)

J. Hinderling, M. W. Sigrist, F. K. Kneubuhl, “Field and Laboratory Experiments on the 8 to 14 μm Spectral Window of the Terrestrial Atmosphere,” Int. J. Infrared Phys. Millimeter Waves 7, 683–713 (1986).
[CrossRef]

1985 (1)

1982 (1)

A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
[CrossRef]

1981 (1)

A. J. Zuckerwar, W. A. Griffin, “Effect of Water Vapour on Sound Absorption in Nitrogen at Low Frequency/Pressure Ratios,” J. Acoust. Soc. Am. 69, 150–154 (1981).
[CrossRef]

1980 (1)

F. E. Hovis, C. M. Moore, “Temperature Dependence of Vibrational Energy Transfer in NH3 and H218O,” J. Chem. Phys. 72, 2397–2402 (1980).
[CrossRef]

1979 (1)

1978 (3)

1971 (1)

1969 (1)

R. L. Taylor, S. Bitterman, Survey of Vibrational Relaxation Data for Processes Important in the CO2-N2 Laser System,” Rev. Mod. Phys. 41, 26–47 (1969).
[CrossRef]

Asman, W. A. H.

J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
[CrossRef]

Bauer, S. H.

S. H. Bauer, J. F. Caballero, R. Curtis, J. R. Wiesenfeld, “Vibrational Relaxation Rates of CO2 (001) with Various Collision Partners for T <300 K,” J. Chem. Phys. 91, 1778–1785 (1987).
[CrossRef]

Beck, S. M.

Bitterman, S.

R. L. Taylor, S. Bitterman, Survey of Vibrational Relaxation Data for Processes Important in the CO2-N2 Laser System,” Rev. Mod. Phys. 41, 26–47 (1969).
[CrossRef]

Brewer, R. J.

Bruce, C. W.

Caballero, J. F.

S. H. Bauer, J. F. Caballero, R. Curtis, J. R. Wiesenfeld, “Vibrational Relaxation Rates of CO2 (001) with Various Collision Partners for T <300 K,” J. Chem. Phys. 91, 1778–1785 (1987).
[CrossRef]

Camac, M.

Coltrin, M. E.

B. D. Kay, T. D. Raymond, M. E. Coltrin, “Observation of Direct Multiquantum Vibrational Excitation in Gas-Surface Scattering: NH3 on Au(111),” Phys. Rev. Lett. 59, 2792–2794 (1990).
[CrossRef]

Curtis, R.

S. H. Bauer, J. F. Caballero, R. Curtis, J. R. Wiesenfeld, “Vibrational Relaxation Rates of CO2 (001) with Various Collision Partners for T <300 K,” J. Chem. Phys. 91, 1778–1785 (1987).
[CrossRef]

Demin, A. I.

A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
[CrossRef]

Erisman, J. W.

J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
[CrossRef]

Gerry, E. T.

Griffin, W. A.

A. J. Zuckerwar, W. A. Griffin, “Effect of Water Vapour on Sound Absorption in Nitrogen at Low Frequency/Pressure Ratios,” J. Acoust. Soc. Am. 69, 150–154 (1981).
[CrossRef]

Harren, F.

F. Harren, “The Photoacoustic Effect, Refined and Applied to Biological Problems,” Thesis, Catholic University of Nijmegen, The Netherlands (1988).

Hinderling, J.

J. Hinderling, M. W. Sigrist, F. K. Kneubuhl, “Field and Laboratory Experiments on the 8 to 14 μm Spectral Window of the Terrestrial Atmosphere,” Int. J. Infrared Phys. Millimeter Waves 7, 683–713 (1986).
[CrossRef]

Hovis, F. E.

F. E. Hovis, C. M. Moore, “Temperature Dependence of Vibrational Energy Transfer in NH3 and H218O,” J. Chem. Phys. 72, 2397–2402 (1980).
[CrossRef]

F. E. Hovis, C. B. Moore, “Vibrational Relaxation of NH3 (ν2),” J. Chem. Phys. 69, 4947–4950 (1978).
[CrossRef]

Ingard, K. U.

P. M. Morse, K. U. Ingard, Theoretical Acoustics (Princeton U.P., 1986).

Kavaya, M. J.

Kay, B. D.

B. D. Kay, T. D. Raymond, M. E. Coltrin, “Observation of Direct Multiquantum Vibrational Excitation in Gas-Surface Scattering: NH3 on Au(111),” Phys. Rev. Lett. 59, 2792–2794 (1990).
[CrossRef]

Kneubuhl, F. K.

J. Hinderling, M. W. Sigrist, F. K. Kneubuhl, “Field and Laboratory Experiments on the 8 to 14 μm Spectral Window of the Terrestrial Atmosphere,” Int. J. Infrared Phys. Millimeter Waves 7, 683–713 (1986).
[CrossRef]

Kritchman, E.

Kudryavtsev, E. M.

A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
[CrossRef]

Letokhov, V. S.

V. P. Zharov, V. S. Letokhov, Laser Opto-Acoustic Spectroscopy (Springer-Verlag, New York, 1986).

Logunov, A. N.

A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
[CrossRef]

Margolis, J. S.

Meyer, P. L.

P. L. Meyer, M. W. Sigrist, “Air-Pollution Monitoring With Mobile CO2-Laser Photo-Acoustic System,” Ph.D. Thesis 8651 ETH Zurich (of P. L. Meyer) (1988).

Moore, C. B.

F. E. Hovis, C. B. Moore, “Vibrational Relaxation of NH3 (ν2),” J. Chem. Phys. 69, 4947–4950 (1978).
[CrossRef]

Moore, C. M.

F. E. Hovis, C. M. Moore, “Temperature Dependence of Vibrational Energy Transfer in NH3 and H218O,” J. Chem. Phys. 72, 2397–2402 (1980).
[CrossRef]

Morse, P. M.

P. M. Morse, K. U. Ingard, Theoretical Acoustics (Princeton U.P., 1986).

Raymond, T. D.

B. D. Kay, T. D. Raymond, M. E. Coltrin, “Observation of Direct Multiquantum Vibrational Excitation in Gas-Surface Scattering: NH3 on Au(111),” Phys. Rev. Lett. 59, 2792–2794 (1990).
[CrossRef]

Rooth, R. A.

R. A. Rooth, A. J. L. Verhage, L. W. Wouters, L. van den Beld, “On the Photo-Acoustic Measurement of Ammonia in the Atmosphere,” in Proceedings, Fourth International Conference on Infrared Physics (ETH, Zurich, 1988), pp. 593–595.

Rosencwaig, A.

A. Rosencwaig, Photoacoustics and Photoacoustic Spectroscopy (Wiley, New York, 1980).

Rothman, L. S.

Shtrikman, S.

Shumate, M. S.

Sigrist, M. W.

J. Hinderling, M. W. Sigrist, F. K. Kneubuhl, “Field and Laboratory Experiments on the 8 to 14 μm Spectral Window of the Terrestrial Atmosphere,” Int. J. Infrared Phys. Millimeter Waves 7, 683–713 (1986).
[CrossRef]

P. L. Meyer, M. W. Sigrist, “Air-Pollution Monitoring With Mobile CO2-Laser Photo-Acoustic System,” Ph.D. Thesis 8651 ETH Zurich (of P. L. Meyer) (1988).

Slanina, J.

J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
[CrossRef]

Slatkine, M.

Sobolev, N. N.

A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
[CrossRef]

Taylor, R. L.

R. L. Taylor, S. Bitterman, Survey of Vibrational Relaxation Data for Processes Important in the CO2-N2 Laser System,” Rev. Mod. Phys. 41, 26–47 (1969).
[CrossRef]

van den Beld, L.

R. A. Rooth, A. J. L. Verhage, L. W. Wouters, L. van den Beld, “On the Photo-Acoustic Measurement of Ammonia in the Atmosphere,” in Proceedings, Fourth International Conference on Infrared Physics (ETH, Zurich, 1988), pp. 593–595.

Verhage, A. J. L.

R. A. Rooth, A. J. L. Verhage, L. W. Wouters, L. van den Beld, “On the Photo-Acoustic Measurement of Ammonia in the Atmosphere,” in Proceedings, Fourth International Conference on Infrared Physics (ETH, Zurich, 1988), pp. 593–595.

Vermetten, A. W. M.

J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
[CrossRef]

Volkov, A. Yu.

A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
[CrossRef]

Wayers-IJpelaan, A.

J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
[CrossRef]

Wiesenfeld, J. R.

S. H. Bauer, J. F. Caballero, R. Curtis, J. R. Wiesenfeld, “Vibrational Relaxation Rates of CO2 (001) with Various Collision Partners for T <300 K,” J. Chem. Phys. 91, 1778–1785 (1987).
[CrossRef]

Wood, A. D.

Wouters, L. W.

R. A. Rooth, A. J. L. Verhage, L. W. Wouters, L. van den Beld, “On the Photo-Acoustic Measurement of Ammonia in the Atmosphere,” in Proceedings, Fourth International Conference on Infrared Physics (ETH, Zurich, 1988), pp. 593–595.

Zharov, V. P.

V. P. Zharov, V. S. Letokhov, Laser Opto-Acoustic Spectroscopy (Springer-Verlag, New York, 1986).

Zuckerwar, A. J.

A. J. Zuckerwar, W. A. Griffin, “Effect of Water Vapour on Sound Absorption in Nitrogen at Low Frequency/Pressure Ratios,” J. Acoust. Soc. Am. 69, 150–154 (1981).
[CrossRef]

Appl. Opt. (5)

Atmos. Environ. (1)

J. W. Erisman, A. W. M. Vermetten, W. A. H. Asman, A. Wayers-IJpelaan, J. Slanina, “Vertical Distribution of Gases and Aerosols: The Behaviour of Ammonia and Related Components in the Lower Atmosphere,” Atmos. Environ. 22, 1153–1160 (1988).
[CrossRef]

Int. J. Infrared Phys. Millimeter Waves (1)

J. Hinderling, M. W. Sigrist, F. K. Kneubuhl, “Field and Laboratory Experiments on the 8 to 14 μm Spectral Window of the Terrestrial Atmosphere,” Int. J. Infrared Phys. Millimeter Waves 7, 683–713 (1986).
[CrossRef]

J. Acoust. Soc. Am. (1)

A. J. Zuckerwar, W. A. Griffin, “Effect of Water Vapour on Sound Absorption in Nitrogen at Low Frequency/Pressure Ratios,” J. Acoust. Soc. Am. 69, 150–154 (1981).
[CrossRef]

J. Chem. Phys. (3)

F. E. Hovis, C. B. Moore, “Vibrational Relaxation of NH3 (ν2),” J. Chem. Phys. 69, 4947–4950 (1978).
[CrossRef]

F. E. Hovis, C. M. Moore, “Temperature Dependence of Vibrational Energy Transfer in NH3 and H218O,” J. Chem. Phys. 72, 2397–2402 (1980).
[CrossRef]

S. H. Bauer, J. F. Caballero, R. Curtis, J. R. Wiesenfeld, “Vibrational Relaxation Rates of CO2 (001) with Various Collision Partners for T <300 K,” J. Chem. Phys. 91, 1778–1785 (1987).
[CrossRef]

J. Opt. Soc. Am. (1)

J. Sov. Laser Res. (U.S.) (1)

A. Yu. Volkov, A. I. Demin, A. N. Logunov, E. M. Kudryavtsev, N. N. Sobolev, “Analysis of Data on the Vibrational Relaxation Constants in CO2-N2-H2O Mixtures and Optimization of a Gasdynamic CO2 Laser,” J. Sov. Laser Res. (U.S.) 3, 148–162 (1982).
[CrossRef]

Phys. Rev. Lett. (1)

B. D. Kay, T. D. Raymond, M. E. Coltrin, “Observation of Direct Multiquantum Vibrational Excitation in Gas-Surface Scattering: NH3 on Au(111),” Phys. Rev. Lett. 59, 2792–2794 (1990).
[CrossRef]

Rev. Mod. Phys. (1)

R. L. Taylor, S. Bitterman, Survey of Vibrational Relaxation Data for Processes Important in the CO2-N2 Laser System,” Rev. Mod. Phys. 41, 26–47 (1969).
[CrossRef]

Other (6)

A. Rosencwaig, Photoacoustics and Photoacoustic Spectroscopy (Wiley, New York, 1980).

P. L. Meyer, M. W. Sigrist, “Air-Pollution Monitoring With Mobile CO2-Laser Photo-Acoustic System,” Ph.D. Thesis 8651 ETH Zurich (of P. L. Meyer) (1988).

R. A. Rooth, A. J. L. Verhage, L. W. Wouters, L. van den Beld, “On the Photo-Acoustic Measurement of Ammonia in the Atmosphere,” in Proceedings, Fourth International Conference on Infrared Physics (ETH, Zurich, 1988), pp. 593–595.

V. P. Zharov, V. S. Letokhov, Laser Opto-Acoustic Spectroscopy (Springer-Verlag, New York, 1986).

F. Harren, “The Photoacoustic Effect, Refined and Applied to Biological Problems,” Thesis, Catholic University of Nijmegen, The Netherlands (1988).

P. M. Morse, K. U. Ingard, Theoretical Acoustics (Princeton U.P., 1986).

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Figures (10)

Fig. 1
Fig. 1

Predicted amplitude R (a) and phase θ (b) of the photo-acoustic signal in air with 360-ppm CO2 and variable water vapor concentration for different modulation frequencies. Excitation at the 9R28 CO2 line (9.23 μm). Amplitude units: 10 = 46 μV/W.

Fig. 2
Fig. 2

Predicted amplitude R and phase θ for air with 340-ppm CO2 as a function of the water vapor concentration. The corresponding experimental data are also plotted; frequency, 560 Hz; excitation, 9R28 CO2 line (9.23 μm).

Fig. 3
Fig. 3

Amplitude R (a) and phase θ (b) of photoacoustic signals computed at four different NH3 concentrations as a function of the water vapor concentration. The CO2 content of the air is taken at 360 ppm, the frequency is 560 Hz, excitation, 9R30 CO2 line (9.22 μm).

Fig. 4
Fig. 4

Absolute value of F for different CO2 concentrations and variable water vapor concentration. The curves are computed for 560 Hz and a laser wavelength of 9.22 μm.

Fig. 5
Fig. 5

Vectorial representation of the computation of the ammonia concentration. The length p a - p b is proportional to the ammonia concentration (x2). The vectors pa and pb are the measured signals at the 9R30 and 9R28 lines, respectively.

Fig. 6
Fig. 6

Cross section of the photoacoustic cell (to scale). The length of the resonator tube is 30 cm.

Fig. 7
Fig. 7

Release of ammonia due to the admission of 1% of water vapor to the calibration gas (25 ppb of NH3 in N2), applied to the gold-coated photoacoustic cell at t = 0. The cell was exposed to 25 ppb of NH3 during 1 h and had reached the final equilibrium value for that concentration (dotted line).

Fig. 8
Fig. 8

Response of the photoacoustic cell made of PFA to variations in the NH3 and H2O concentrations. Trace 1 shows the response to 25-ppb NH3 added to dry N2. The ideal response is dashed. Addition of 1% H2O to 25-ppb NH3 is shown by trace 2. The flow rate is 1 liter/min, the total volume of the cell is ~0.5 liter.

Fig. 9
Fig. 9

Schematic view of the field instrument.

Fig. 10
Fig. 10

Temporal variations of the hourly averaged concentrations of H2O (a) and NH3 (b) measured during 4 weeks on a heath in Elspeet, The Netherlands. The enlarged view (c) shows the initial NH3 data taken at 6-min intervals on the third and fourth days of the measurements (26 Apr., 13 h; 28 Apr., 15 h, 1989).

Tables (1)

Tables Icon

Table 1 Relaxation Rates for Various V–T Transfers, Assuming Standard Atmospheric Conditions: 21% O2, 78% N2, 350-ppm CO2, 0% H2O and 1% H2O

Equations (24)

Equations on this page are rendered with MathJax. Learn more.

d H d t = ( α 1 x 1 + α 2 x 2 + α 3 x 3 ) I ( t ) - d E 4 d t - ( H - H ( o ) τ s ) ,
d E 4 d t = E 4 ( o ) - E 4 ( t ) τ 4 + β α 3 x 3 I ( t ) .
τ 4 - 1 = ( x 1 τ 31 - 1 + x 4 τ 34 - 1 + x 5 τ 35 - 1 ) x 3 x 4 + x 1 τ 41 - 1 + x 5 τ 45 - 1 .
E 4 ( t ) = E 4 ( o ) exp ( - t τ 4 ) + ( β α 3 x 3 I o τ 4 ) { 1 - exp ( - t τ 4 ) + [ exp ( i ω t ) - exp ( - t τ 4 ) 1 + i ω τ 4 ] } .
E 4 ( t ) = β α 3 x 3 τ 4 I o [ 1 + exp ( i ω t ) ] 1 + i ω τ 4 ,
d E 4 ( t ) d t = β α 3 x 3 i ω τ 4 I o exp ( i ω t ) 1 + i ω τ 4 .
H ( t ) = H ( o ) + I o τ s ( α 1 x 1 + α 2 x 2 + α 3 x 3 ) [ 1 - exp ( - t τ s ) ] + I 0 τ s 1 + i ω τ s ( α 1 x 1 + α 2 x 2 - α 3 x 3 β i ω τ 4 1 + i ω τ 4 ) [ exp ( i ω t ) - exp ( - t τ s ) ] .
p ( t ) = A I o i ω { α 1 x 1 + α 2 x 2 + α 3 x 3 ( 1 - β i ω τ 4 1 + i ω τ 4 ) } exp ( i ω t ) .
R = A I o ω | ( α 1 x 1 + α 2 x 2 + ( 1 - β ) α 3 x 3 ) 2 + ( α 1 x 1 + α 2 x 2 + α 3 x 3 ) 2 ( ω τ 4 ) - 2 [ 1 + ( ω τ 4 ) 2 ] ( ω τ 4 ) - 2 | 1 / 2 ,
θ = arctan - β α 3 x 3 ( ω τ 4 ) - 1 ( α 1 x 1 + α 2 x 2 + α 3 x 3 ) [ 1 + ( ω τ 4 ) 2 ( ω τ 4 ) - 2 - β α 3 x 3 ] .
d p d t ( ω τ 4 1 ) = A I o ( α 1 x 1 + α 2 x 2 + α 3 x 3 ) exp ( i ω t ) , R ( ω τ 4 1 ) = A I o ω ( α 1 x 1 + α 2 x 2 + α 3 x 3 ) , θ ( ω τ 4 1 ) = arctan ( - β α 3 x 3 ω τ 4 α 1 x 1 + α 2 x 2 + α 3 x 3 ) .
d p d t ( ω τ 4 1 ) = A I o ( α 1 x 1 + α 2 x 2 - ( β - 1 ) α 3 x 3 ) exp ( i ω t ) , R ( ω τ 4 1 ) = A I o ω α 1 x 1 + α 2 x 2 - ( β - 1 ) α 3 x 3 , θ ( ω τ 4 1 ) = arctan ( - β α 3 x 3 ( ω τ 4 ) - 1 α 1 x 1 + α 2 x 2 - ( β - 1 ) α 3 x 3 ) .
R ( ω τ 4 1 ) = A I o ω ( β - 1 ) α 3 x 3 .
d p d t ( ω τ 4 1 ) = - A I o ( β - 1 ) α 3 x 3 exp ( i ω t ) , θ ( ω τ 4 1 ) = π - arctan ( β β - 1 1 ω τ 4 ) ,
p a = A I o i ω [ α 1 x 1 + α 2 x 2 + α 3 a x 3 F ( ω , x 1 , x 3 ) ] ,
p b = A I o i ω [ α 1 x 1 + α 3 b x 3 F ( ω , x 1 , x 3 ) ] .
F = 1 - β i ω τ 4 1 + i ω τ 4 ,
p a - p b = A I o ω α 2 x 2 - α 3 b x 3 F ( ω , x 1 , x 3 ) .
p a - p b = ( R a 2 + R b 2 - 2 R a R b cos ( θ a - θ b ) ) 1 / 2 .
p b = A I o i ω { α 1 x 1 + α 3 a x 3 F ( ω , x 1 , x 3 ) } .
p a - p b = A I o i ω α 2 x 2 .
p c - p b = A I o ω ( α 3 c - α 3 b ) x 3 F ( ω , x 1 , x 3 ) .
c s = c so ( T T o ) 1 / 2 ,
c s = c so [ 1 - p w p air ( γ w γ air - 5 8 ) ] 1 / 2 .

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