Abstract

We describe the development of a room-temperature diode sensor for in situ monitoring of combustion-generated NO. The sensor is based on a near-IR diode laser operating near 1.8 µm, which probes isolated transitions in the second overtone (3,0) absorption band of NO. Based on absorption cell data, the sensitivity for ambient atmospheric pressure conditions is of the order of 30 parts in 106 by volume for a meter path (ppmv–m), assuming a minimum measurable absorbance of 10-5. Initial H2 –air flame measurements are complicated by strong water vapor absorption features that constrain the available gain and dynamic range of the present detection system. Preliminary results suggest that detection limits in this environment of the order of 140 ppmv–m could be achieved with optimum baseline correction.

© 1997 Optical Society of America

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References

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  1. M. G. Allen, W. J. Kessler, “Simultaneous water vapor concentration and temperature measurements using 1.31 µm diode lasers,” AIAA J. 34, 384–488 (1996).
    [CrossRef]
  2. D. S. Baer, V. Nagali, E. R. Furlong, R. K. Hanson, M. E. Newfield, “Scanned- and fixed-wavelength absorption diagnostics for combustion measurements using multiplexed diode lasers,” AIAA J. 34, 489–493 (1996).
    [CrossRef]
  3. D. M. Sonnenfroh, M. G. Allen, “Ultrasensitive, visible tunable diode laser detection of NO2,” Appl. Opt. 35, 4053–4058 (1996).
    [CrossRef] [PubMed]
  4. R. M. Mihalcea, D. S. Baer, R. K. Hanson, “Tunable diode-laser absorption measurements of NO2 near 670 and 395 nm,” Appl. Opt. 35, 4059–4063 (1996).
    [CrossRef] [PubMed]
  5. V. Nagali, S. I. Chou, D. S. Baer, R. K. Hanson, J. Segall, “Tunable diode-laser absorption measurements of methane at elevated temperatures,” Appl. Opt. 35, 4026–4032 (1996).
    [CrossRef] [PubMed]
  6. M. F. Miller, W. J. Kessler, M. G. Allen, “Diode laser-based air mass flux sensor for subsonic aeropropulsion inlets,” Appl. Opt. 35, 4905–4912 (1996).
    [CrossRef] [PubMed]
  7. D. M. Sonnenfroh, M. G. Allen, “Observations of CO and CO2 absorption near 1.57 microns using an external cavity diode laser,” Appl. Opt. 36, 3298–3300 (1997).
    [CrossRef] [PubMed]
  8. J. A. Silver, D. S. Kane, P. S. Greenberg, “Quantitative species measurements in microgravity flames with near-IR diode lasers,” Appl. Opt. 34, 2787–2801 (1995).
    [CrossRef] [PubMed]
  9. D. B. Oh, A. C. Stanton, “Measurements of nitric oxide using an antimonide diode laser,” Appl. Opt. 36, 3294–3297 (1997).
    [CrossRef] [PubMed]
  10. G. A. Mann, C. D. Hause, “Magnetic rotation spectra of nitric oxide in the near infrared,” J. Chem. Phys. 33, 1117–1123 (1960).
    [CrossRef]
  11. C. Amiot, “The infrared emission spectrum of NO: analysis of the Δv = 3 sequence up to v = 22,” J. Mol. Spectrosc. 94, 150–172 (1982).
    [CrossRef]
  12. K. W. Holtzclaw, W. T. Rawlins, B. D. Green, “The effects of centrifugal distortion on the infrared radiative transition probabilities of NO (X 2II),” J. Quant. Spectrosc. Radiat. Transfer 55, 481–492 (1996).
    [CrossRef]
  13. L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).
  14. P. C. D. Hobbs, “Shot noise limited optical measurements at baseband with noisy laser,” in Laser Noise, R. Roy, ed., Proc. SPIE1376, 216–221 (1991).
    [CrossRef]
  15. K. L. Haller, P. C. D. Hobbs, “Double beam laser absorption spectroscopy: shot noise-limited performance at baseband with a novel electronic noise canceller,” in Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, B. L. Fearey, ed., Proc. SPIE1435, 298–309 (1991).
    [CrossRef]
  16. P. C. D. Hobbs, “Ultrasensitive laser measurements without tears,” Appl. Opt. 36, 903–920 (1997).
    [CrossRef] [PubMed]
  17. M. G. Allen, K. L. Carleton, S. J. Davis, W. J. Kessler, C. E. Otis, D. A. Palombo, D. M. Sonnenfroh, “Ultra-sensitive dual-beam absorption and gain spectroscopy: applications for near-infrared and visible diode laser sensors,” Appl. Opt. 34, 3240–3249 (1995).
    [CrossRef] [PubMed]
  18. D. T. Cassidy, L. J. Bonnell, “Trace gas detection with short-external-cavity InGaAsP diode laser transmitter modules operating at 1.58 µm,” Appl. Opt. 27, 2688–2693 (1988).
    [CrossRef] [PubMed]
  19. A. S. Pine, J. W. C. Johns, A. G. Robiette, “Λ-doubling in the v = 2 ← 0 overtone band in the infrared spectrum of NO,” J. Mol. Spectrosc. 74, 52–69 (1979).
    [CrossRef]
  20. V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
    [CrossRef]

1997 (3)

1996 (7)

K. W. Holtzclaw, W. T. Rawlins, B. D. Green, “The effects of centrifugal distortion on the infrared radiative transition probabilities of NO (X 2II),” J. Quant. Spectrosc. Radiat. Transfer 55, 481–492 (1996).
[CrossRef]

M. G. Allen, W. J. Kessler, “Simultaneous water vapor concentration and temperature measurements using 1.31 µm diode lasers,” AIAA J. 34, 384–488 (1996).
[CrossRef]

D. S. Baer, V. Nagali, E. R. Furlong, R. K. Hanson, M. E. Newfield, “Scanned- and fixed-wavelength absorption diagnostics for combustion measurements using multiplexed diode lasers,” AIAA J. 34, 489–493 (1996).
[CrossRef]

D. M. Sonnenfroh, M. G. Allen, “Ultrasensitive, visible tunable diode laser detection of NO2,” Appl. Opt. 35, 4053–4058 (1996).
[CrossRef] [PubMed]

R. M. Mihalcea, D. S. Baer, R. K. Hanson, “Tunable diode-laser absorption measurements of NO2 near 670 and 395 nm,” Appl. Opt. 35, 4059–4063 (1996).
[CrossRef] [PubMed]

V. Nagali, S. I. Chou, D. S. Baer, R. K. Hanson, J. Segall, “Tunable diode-laser absorption measurements of methane at elevated temperatures,” Appl. Opt. 35, 4026–4032 (1996).
[CrossRef] [PubMed]

M. F. Miller, W. J. Kessler, M. G. Allen, “Diode laser-based air mass flux sensor for subsonic aeropropulsion inlets,” Appl. Opt. 35, 4905–4912 (1996).
[CrossRef] [PubMed]

1995 (2)

1994 (1)

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

1988 (1)

1982 (1)

C. Amiot, “The infrared emission spectrum of NO: analysis of the Δv = 3 sequence up to v = 22,” J. Mol. Spectrosc. 94, 150–172 (1982).
[CrossRef]

1979 (1)

A. S. Pine, J. W. C. Johns, A. G. Robiette, “Λ-doubling in the v = 2 ← 0 overtone band in the infrared spectrum of NO,” J. Mol. Spectrosc. 74, 52–69 (1979).
[CrossRef]

1960 (1)

G. A. Mann, C. D. Hause, “Magnetic rotation spectra of nitric oxide in the near infrared,” J. Chem. Phys. 33, 1117–1123 (1960).
[CrossRef]

Allen, M. G.

Amiot, C.

C. Amiot, “The infrared emission spectrum of NO: analysis of the Δv = 3 sequence up to v = 22,” J. Mol. Spectrosc. 94, 150–172 (1982).
[CrossRef]

Badaoui, M.

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

Baer, D. S.

Bonnell, L. J.

Camy-Peyret, C.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Carleton, K. L.

Cassidy, D. T.

Chou, S. I.

Coudert, L.

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

Dana, V.

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

Davis, S. J.

Flaud, J.-M.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Furlong, E. R.

D. S. Baer, V. Nagali, E. R. Furlong, R. K. Hanson, M. E. Newfield, “Scanned- and fixed-wavelength absorption diagnostics for combustion measurements using multiplexed diode lasers,” AIAA J. 34, 489–493 (1996).
[CrossRef]

Gamache, R. R.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Goorvetch, D.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Green, B. D.

K. W. Holtzclaw, W. T. Rawlins, B. D. Green, “The effects of centrifugal distortion on the infrared radiative transition probabilities of NO (X 2II),” J. Quant. Spectrosc. Radiat. Transfer 55, 481–492 (1996).
[CrossRef]

Greenberg, P. S.

Guelachvili, G.

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

Haller, K. L.

K. L. Haller, P. C. D. Hobbs, “Double beam laser absorption spectroscopy: shot noise-limited performance at baseband with a novel electronic noise canceller,” in Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, B. L. Fearey, ed., Proc. SPIE1435, 298–309 (1991).
[CrossRef]

Hanson, R. K.

Hause, C. D.

G. A. Mann, C. D. Hause, “Magnetic rotation spectra of nitric oxide in the near infrared,” J. Chem. Phys. 33, 1117–1123 (1960).
[CrossRef]

Hawkins, R. L.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Hobbs, P. C. D.

P. C. D. Hobbs, “Ultrasensitive laser measurements without tears,” Appl. Opt. 36, 903–920 (1997).
[CrossRef] [PubMed]

K. L. Haller, P. C. D. Hobbs, “Double beam laser absorption spectroscopy: shot noise-limited performance at baseband with a novel electronic noise canceller,” in Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, B. L. Fearey, ed., Proc. SPIE1435, 298–309 (1991).
[CrossRef]

P. C. D. Hobbs, “Shot noise limited optical measurements at baseband with noisy laser,” in Laser Noise, R. Roy, ed., Proc. SPIE1376, 216–221 (1991).
[CrossRef]

Holtzclaw, K. W.

K. W. Holtzclaw, W. T. Rawlins, B. D. Green, “The effects of centrifugal distortion on the infrared radiative transition probabilities of NO (X 2II),” J. Quant. Spectrosc. Radiat. Transfer 55, 481–492 (1996).
[CrossRef]

Johns, J. W. C.

A. S. Pine, J. W. C. Johns, A. G. Robiette, “Λ-doubling in the v = 2 ← 0 overtone band in the infrared spectrum of NO,” J. Mol. Spectrosc. 74, 52–69 (1979).
[CrossRef]

Kane, D. S.

Kessler, W. J.

Le Roy, F.

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

Mandin, J.-Y.

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

Mann, G. A.

G. A. Mann, C. D. Hause, “Magnetic rotation spectra of nitric oxide in the near infrared,” J. Chem. Phys. 33, 1117–1123 (1960).
[CrossRef]

McCann, A.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Mihalcea, R. M.

Miller, M. F.

Nagali, V.

V. Nagali, S. I. Chou, D. S. Baer, R. K. Hanson, J. Segall, “Tunable diode-laser absorption measurements of methane at elevated temperatures,” Appl. Opt. 35, 4026–4032 (1996).
[CrossRef] [PubMed]

D. S. Baer, V. Nagali, E. R. Furlong, R. K. Hanson, M. E. Newfield, “Scanned- and fixed-wavelength absorption diagnostics for combustion measurements using multiplexed diode lasers,” AIAA J. 34, 489–493 (1996).
[CrossRef]

Newfield, M. E.

D. S. Baer, V. Nagali, E. R. Furlong, R. K. Hanson, M. E. Newfield, “Scanned- and fixed-wavelength absorption diagnostics for combustion measurements using multiplexed diode lasers,” AIAA J. 34, 489–493 (1996).
[CrossRef]

Oh, D. B.

Otis, C. E.

Palombo, D. A.

Pine, A. S.

A. S. Pine, J. W. C. Johns, A. G. Robiette, “Λ-doubling in the v = 2 ← 0 overtone band in the infrared spectrum of NO,” J. Mol. Spectrosc. 74, 52–69 (1979).
[CrossRef]

Rawlins, W. T.

K. W. Holtzclaw, W. T. Rawlins, B. D. Green, “The effects of centrifugal distortion on the infrared radiative transition probabilities of NO (X 2II),” J. Quant. Spectrosc. Radiat. Transfer 55, 481–492 (1996).
[CrossRef]

Robiette, A. G.

A. S. Pine, J. W. C. Johns, A. G. Robiette, “Λ-doubling in the v = 2 ← 0 overtone band in the infrared spectrum of NO,” J. Mol. Spectrosc. 74, 52–69 (1979).
[CrossRef]

Rothman, L. S.

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Schroeder, J.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Segall, J.

Selby, J. E. A.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

Silver, J. A.

Sonnenfroh, D. M.

Stanton, A. C.

Watson, R. B.

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

AIAA J. (2)

M. G. Allen, W. J. Kessler, “Simultaneous water vapor concentration and temperature measurements using 1.31 µm diode lasers,” AIAA J. 34, 384–488 (1996).
[CrossRef]

D. S. Baer, V. Nagali, E. R. Furlong, R. K. Hanson, M. E. Newfield, “Scanned- and fixed-wavelength absorption diagnostics for combustion measurements using multiplexed diode lasers,” AIAA J. 34, 489–493 (1996).
[CrossRef]

Appl. Opt. (10)

D. M. Sonnenfroh, M. G. Allen, “Ultrasensitive, visible tunable diode laser detection of NO2,” Appl. Opt. 35, 4053–4058 (1996).
[CrossRef] [PubMed]

R. M. Mihalcea, D. S. Baer, R. K. Hanson, “Tunable diode-laser absorption measurements of NO2 near 670 and 395 nm,” Appl. Opt. 35, 4059–4063 (1996).
[CrossRef] [PubMed]

V. Nagali, S. I. Chou, D. S. Baer, R. K. Hanson, J. Segall, “Tunable diode-laser absorption measurements of methane at elevated temperatures,” Appl. Opt. 35, 4026–4032 (1996).
[CrossRef] [PubMed]

M. F. Miller, W. J. Kessler, M. G. Allen, “Diode laser-based air mass flux sensor for subsonic aeropropulsion inlets,” Appl. Opt. 35, 4905–4912 (1996).
[CrossRef] [PubMed]

D. M. Sonnenfroh, M. G. Allen, “Observations of CO and CO2 absorption near 1.57 microns using an external cavity diode laser,” Appl. Opt. 36, 3298–3300 (1997).
[CrossRef] [PubMed]

J. A. Silver, D. S. Kane, P. S. Greenberg, “Quantitative species measurements in microgravity flames with near-IR diode lasers,” Appl. Opt. 34, 2787–2801 (1995).
[CrossRef] [PubMed]

D. B. Oh, A. C. Stanton, “Measurements of nitric oxide using an antimonide diode laser,” Appl. Opt. 36, 3294–3297 (1997).
[CrossRef] [PubMed]

P. C. D. Hobbs, “Ultrasensitive laser measurements without tears,” Appl. Opt. 36, 903–920 (1997).
[CrossRef] [PubMed]

M. G. Allen, K. L. Carleton, S. J. Davis, W. J. Kessler, C. E. Otis, D. A. Palombo, D. M. Sonnenfroh, “Ultra-sensitive dual-beam absorption and gain spectroscopy: applications for near-infrared and visible diode laser sensors,” Appl. Opt. 34, 3240–3249 (1995).
[CrossRef] [PubMed]

D. T. Cassidy, L. J. Bonnell, “Trace gas detection with short-external-cavity InGaAsP diode laser transmitter modules operating at 1.58 µm,” Appl. Opt. 27, 2688–2693 (1988).
[CrossRef] [PubMed]

J. Chem. Phys. (1)

G. A. Mann, C. D. Hause, “Magnetic rotation spectra of nitric oxide in the near infrared,” J. Chem. Phys. 33, 1117–1123 (1960).
[CrossRef]

J. Mol. Spectrosc. (3)

C. Amiot, “The infrared emission spectrum of NO: analysis of the Δv = 3 sequence up to v = 22,” J. Mol. Spectrosc. 94, 150–172 (1982).
[CrossRef]

A. S. Pine, J. W. C. Johns, A. G. Robiette, “Λ-doubling in the v = 2 ← 0 overtone band in the infrared spectrum of NO,” J. Mol. Spectrosc. 74, 52–69 (1979).
[CrossRef]

V. Dana, J.-Y. Mandin, L. Coudert, M. Badaoui, F. Le Roy, G. Guelachvili, L. S. Rothman, “Λ-splittings and line intensities in the 2 ← 1 hot band of nitric oxide,” J. Mol. Spectrosc. 165, 525–540 (1994).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer (1)

K. W. Holtzclaw, W. T. Rawlins, B. D. Green, “The effects of centrifugal distortion on the infrared radiative transition probabilities of NO (X 2II),” J. Quant. Spectrosc. Radiat. Transfer 55, 481–492 (1996).
[CrossRef]

Other (3)

L. S. Rothman, R. B. Watson, R. R. Gamache, D. Goorvetch, R. L. Hawkins, J. E. A. Selby, C. Camy-Peyret, J.-M. Flaud, J. Schroeder, A. McCann, “HITEMP, the high-temperature molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transfer (to be published).

P. C. D. Hobbs, “Shot noise limited optical measurements at baseband with noisy laser,” in Laser Noise, R. Roy, ed., Proc. SPIE1376, 216–221 (1991).
[CrossRef]

K. L. Haller, P. C. D. Hobbs, “Double beam laser absorption spectroscopy: shot noise-limited performance at baseband with a novel electronic noise canceller,” in Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, B. L. Fearey, ed., Proc. SPIE1435, 298–309 (1991).
[CrossRef]

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Figures (10)

Fig. 1
Fig. 1

Calculated absorption spectra for the (3,0) band of NO at (a) 300 K, (b) 800 K, (c) 2000 K.

Fig. 2
Fig. 2

(a) FTIR absorption spectrum (solid curve) of the (3,0) band for 169-Torr NO at 295 K, 5.8-m path length, and 10 scans averaged compared with calculated spectrum (dotted curve). (b) Expanded scale. The spectral region accessible by the diode laser is 5523 to 5535 cm-1.

Fig. 3
Fig. 3

Comparison of experimental FTIR (solid curve) and Hitemp-predicted (dotted curve) spectra of H2O vapor at 2340 K. The experimental spectrum is an average of 20 spectra obtained for a path of 41 cm. The Hitemp spectrum was convolved with a Gaussian instrumental function having a FWHM of 0.75 cm-1.

Fig. 4
Fig. 4

Survey spectra for 742-Torr 10% NO/N2 (0.5-m path) and 15% relative humidity water vapor (ambient pressure, 0.14-m path) at 296 K.

Fig. 5
Fig. 5

Spectrum of the P11 (6) + P21 (6) Λ-doublet pair for 20-Torr NO (0.5-m path, 296 K). The radiometric signal is plotted along with the deconvolved fits for the two Λ-doublet components, as well as their sum. The frequency scale is approximate.

Fig. 6
Fig. 6

Integrated absorbance of the P11 (6) + P21 (6) Λ-doublet pair versus partial pressure of NO. The sample was 10% NO/N2. Other conditions were 0.5-m path and 296 K.

Fig. 7
Fig. 7

Experimental absorption spectra near the NO P11 (6) + P21 (6) Λ-doublet pair: (a) with 6.3% NO seeding in the precombustion gases, and (b) without NO seeding. The spectra are an average of 100 sweeps acquired at a 10-Hz laser scan rate and over a path of 0.68 m. The equivalence ratio was 0.25 and the flame temperature was ∼1050 K.

Fig. 8
Fig. 8

Experimental difference absorption spectrum for the NO P11 (6) + P21 (6) Λ-doublet pair. The NO seeding ratio was 6.3%.

Fig. 9
Fig. 9

Variation of peak absorption for the NO P11 (6) + P21 (6) Λ-doublet pair with NO seeding. Conditions were the same as for Fig. 8. Dashed line is the calculated absorption from the measured seed ratio and theoretical line strengths.

Fig. 10
Fig. 10

Experimental difference absorption spectrum for the NO P11 (6) + P21 (6) Λ-doublet pair following fast Fourier-transform processing to remove interference fringes. The NO seeding ratio was 0.9%.

Tables (2)

Tables Icon

Table 1 Candidate (3,0) Band Absorption Lines

Tables Icon

Table 2 Comparison of Measured and Calculated Line Strengths

Metrics