Abstract

A quantum-cascade laser operating at a wavelength of 8.1 µm was used for high-sensitivity absorption spectroscopy of methane CH4. The laser frequency was continuously scanned with current over more than 3 cm-1, and absorption spectra of the CH4 ν4 P branch were recorded. The measured laser linewidth was 50 MHz. A CH4 concentration of 15.6 parts in 106 ppm in 50 Torr of air was measured in a 43-cm path length with ±0.5ppm accuracy when the signal was averaged over 400 scans. The minimum detectable absorption in such direct absorption measurements is estimated to be 1.1×10-4. The content of  13CH4 and CH3D species in a CH4 sample was determined.

© 1999 Optical Society of America

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References

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  1. K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
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1999 (2)

1998 (3)

1997 (2)

J. Faist, C. Gmachl, F. Capasso, C. Sirtori, D. L. Sivco, J. N. Baillargeon, and A. Y. Cho, Appl. Phys. Lett. 70, 2670 (1997).
[CrossRef]

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

1994 (1)

1981 (1)

A. J. Robiette, J. Mol. Spectrosc. 86, 143 (1981).
[CrossRef]

1957 (1)

H. Graig, Geochim. Cosmochim. Acta 12, 133 (1957).
[CrossRef]

Arbore, M.

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

Baillargeon, J. N.

Bergamaschi, P.

Boardman, L.

C. Oppenheimer, P. Francis, M. Burton, A. J. H. Maciejewski, and L. Boardman, Appl. Phys. B 67, 505 (1998).
[CrossRef]

Burton, M.

C. Oppenheimer, P. Francis, M. Burton, A. J. H. Maciejewski, and L. Boardman, Appl. Phys. B 67, 505 (1998).
[CrossRef]

Cai, S.

Capasso, F.

Cho, A. Y.

Dlugokencky, E. J.

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

Faist, J.

K. Namjou, S. Cai, E. A. Whittaker, J. Faist, C. Gmachl, F. Capasso, D. L. Sivco, and A. Y. Cho, Opt. Lett. 23, 219 (1998).
[CrossRef]

J. Faist, C. Gmachl, F. Capasso, C. Sirtori, D. L. Sivco, J. N. Baillargeon, and A. Y. Cho, Appl. Phys. Lett. 70, 2670 (1997).
[CrossRef]

Fejer, M. M.

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

Fontes, J. Ch.

P. Fritz and J. Ch. Fontes, Handbook of Environmental Isotope Geochemistry (Elsevier, New York, 1980), Vol. 1, pp. 1–19.

Francis, P.

C. Oppenheimer, P. Francis, M. Burton, A. J. H. Maciejewski, and L. Boardman, Appl. Phys. B 67, 505 (1998).
[CrossRef]

Fritz, P.

P. Fritz and J. Ch. Fontes, Handbook of Environmental Isotope Geochemistry (Elsevier, New York, 1980), Vol. 1, pp. 1–19.

Gmachl, C.

Graig, H.

H. Graig, Geochim. Cosmochim. Acta 12, 133 (1957).
[CrossRef]

Harren, F. J. M.

Harris, G. W.

Hartman, J. S.

Hollberg, L. W.

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

Hutchinson, A. L.

Kelly, J. F.

Maciejewski, A. J. H.

C. Oppenheimer, P. Francis, M. Burton, A. J. H. Maciejewski, and L. Boardman, Appl. Phys. B 67, 505 (1998).
[CrossRef]

Namjou, K.

Oomens, J.

Oppenheimer, C.

C. Oppenheimer, P. Francis, M. Burton, A. J. H. Maciejewski, and L. Boardman, Appl. Phys. B 67, 505 (1998).
[CrossRef]

Paldus, B. A.

Parker, D. H.

Petrov, K. P.

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

Robiette, A. J.

A. J. Robiette, J. Mol. Spectrosc. 86, 143 (1981).
[CrossRef]

Schupp, M.

Sharpe, S. W.

Sirtori, C.

J. Faist, C. Gmachl, F. Capasso, C. Sirtori, D. L. Sivco, J. N. Baillargeon, and A. Y. Cho, Appl. Phys. Lett. 70, 2670 (1997).
[CrossRef]

Sivco, D. L.

Spence, T. G.

Tittel, F. K.

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

Waltman, S.

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

Whittaker, E. A.

Zare, R. N.

Appl. Opt. (1)

Appl. Phys. B (2)

K. P. Petrov, S. Waltman, E. J. Dlugokencky, M. Arbore, M. M. Fejer, F. K. Tittel, and L. W. Hollberg, Appl. Phys. B 64, 567 (1997).
[CrossRef]

C. Oppenheimer, P. Francis, M. Burton, A. J. H. Maciejewski, and L. Boardman, Appl. Phys. B 67, 505 (1998).
[CrossRef]

Appl. Phys. Lett. (1)

J. Faist, C. Gmachl, F. Capasso, C. Sirtori, D. L. Sivco, J. N. Baillargeon, and A. Y. Cho, Appl. Phys. Lett. 70, 2670 (1997).
[CrossRef]

Geochim. Cosmochim. Acta (1)

H. Graig, Geochim. Cosmochim. Acta 12, 133 (1957).
[CrossRef]

J. Mol. Spectrosc. (1)

A. J. Robiette, J. Mol. Spectrosc. 86, 143 (1981).
[CrossRef]

Opt. Lett. (3)

Phys. World (1)

F. Capasso, C. Gmachl, D. L. Sivco, and A. Y. Cho, Phys. World 12, 27 (1999).

Other (2)

P. Fritz and J. Ch. Fontes, Handbook of Environmental Isotope Geochemistry (Elsevier, New York, 1980), Vol. 1, pp. 1–19.

“NIST Database for the Isotopic Composition of Selected Atmospheric Constituents,” http://deuterium.nist.gov .

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Figures (4)

Fig. 1
Fig. 1

Schematic of the experimental arrangement.

Fig. 2
Fig. 2

Power on the detector versus QC laser current. The dip in the curve marked with the arrow is due to absorption by water vapor in the air. The dotted curves show power in each of the two laser modes.

Fig. 3
Fig. 3

(a) Simulated absorption spectrum of CH4 (6.5 mTorr, 43 cm) and (b) measured spectrum for the same conditions. The false absorption lines that appear because of the two-mode lasing are marked with asterisks. (c) Measured spectrum of 20 ppm of CH4 in 50 Torr of air. Inset, the Voigt fit of the strongest absorption line. The path length is 43 cm for all three spectra.

Fig. 4
Fig. 4

(a) Absorption lines used to define the  13C content in the CH4 sample. (b) Absorption line of the deuterated CH4. The open circles represent the measured data, and the solid curves represent their Voigt fitting.

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