Abstract

Raman measurements of two common gases are made using a simple multipass capillary Raman cell (MCC) coupled to an unfiltered 18 around 1 fiber-optic Raman probe. The MCC, which is fabricated by chemical deposition of silver on the inner walls of a 2mm inner diameter glass capillary tube, gives up to 20-fold signal enhancements for nonabsorbing gases. The device is relatively small and suitable for remote and in situ Raman measurements with optical fibers. The optical behavior of the MCC is similar to previously described liquid-core waveguides and hollow metal-coated waveguides used for laser transmission, but unlike the former devices, the MCC is generally applicable to a very wide range of nonabsorbing gases.

© 2008 Optical Society of America

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References

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2008 (1)

2002 (1)

2001 (2)

M. J. Pelletier and R. Altkorn, “Raman sensitivity enhancement for aqueous protein samples using a liquid-core optical-fiber cell,” Anal. Chem. 73, 1393-1397 (2001).
[CrossRef] [PubMed]

R. Altkorn, M. D. Malinsky, R. P. Van Duyne, and I. Koev, “Intensity considerations in liquid core optical fiber Raman spectroscopy,” Appl. Spectrosc. 55, 373-381 (2001).
[CrossRef]

1998 (1)

1997 (1)

1992 (1)

1987 (1)

1980 (1)

1977 (1)

1975 (1)

1972 (1)

1945 (1)

G. Herzberg, Infrared and Raman Spectra of Polyatomic Molecules (Van Nostrand Reinhold, 1945).

Adams, F. W.

Adler-Golden, S. M.

Altkorn, R.

Angel, S. M.

Berg, J. M.

Bien, F.

Byer, R. L.

Carter, J. C.

Chan, J. W-J.

Cheng, W. K.

Fountain, A. W.

Gersh, M. E.

Goldstein, N.

Hackett, C. E.

Herzberg, G.

G. Herzberg, Infrared and Raman Spectra of Polyatomic Molecules (Van Nostrand Reinhold, 1945).

Hill, D. D.

Hill, R. A.

Koev, I.

Litorja, M.

Malinsky, M. D.

Mann, C. K.

Matthew, M. W.

McCreery, R. L.

McFarlan, J. T.

Mulac, A. J.

Pearman, W. F.

Pelletier, M. J.

M. J. Pelletier and R. Altkorn, “Raman sensitivity enhancement for aqueous protein samples using a liquid-core optical-fiber cell,” Anal. Chem. 73, 1393-1397 (2001).
[CrossRef] [PubMed]

Rau, K. C.

Schwab, S. D.

Stone, J.

Trutna, W. R.

Van Duyne, R. P.

Veirs, K.

Vickers, T. J.

Walrafen, G. E.

Worl, L. A.

Anal. Chem. (1)

M. J. Pelletier and R. Altkorn, “Raman sensitivity enhancement for aqueous protein samples using a liquid-core optical-fiber cell,” Anal. Chem. 73, 1393-1397 (2001).
[CrossRef] [PubMed]

Appl. Opt. (4)

Appl. Spectrosc. (7)

Other (1)

G. Herzberg, Infrared and Raman Spectra of Polyatomic Molecules (Van Nostrand Reinhold, 1945).

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Figures (6)

Fig. 1
Fig. 1

Experimental setup for the collection of Raman scatter. N 2 , CO 2 , and CH 4 flow rates are controlled by the MFC.

Fig. 2
Fig. 2

Measured power transmittance at the laser wavelength versus capillary length (circles). The solid curve is a fit using Eq. (2) and gives a loss coefficient at the laser wavelength of 0.03 cm 1 .

Fig. 3
Fig. 3

Relative Raman signal measured for N 2 in the backscatter geometry versus the capillary length (circles). The solid curve is a fit using Eq. (4) with a loss coefficient of 0.03 for both the Raman and the laser wavelengths. The upper dashed curve and the lower dash–dot curve are fits using Eq. (4) with a laser wavelength loss coefficient of 0.03 cm 1 but with Raman loss coefficients of 0.025 and 0.035 cm 1 , respectively.

Fig. 4
Fig. 4

Performance of a MCC measuring 2 mm × 4 mm × 496 mm in the measurement of N 2 . Here the dramatic 20 -fold increase in the peak intensity of N 2 by direct coupling the 18@1 probe (a) to the MCC and (b) to the probe alone is shown.

Fig. 5
Fig. 5

Calibration curve for CO 2 constructed using MFCs, 2 mm × 4 mm × 496 mm MCC, and an 18@1 fiber-optic probe. The insert shows the average of five spectra at 0.74% CO 2 . L D calculated using this data is 0.3%.

Fig. 6
Fig. 6

Calibration curve for CH 4 constructed using MFCs, 2 mm × 4 mm × 496 mm MCC, and an 18@1 fiber probe. The error bars denote ± 3 standard deviations of the peak intensity. The insert shows the average of five spectra at 0.25% CH 4 . L D calculated using this data is 0.02%.

Equations (4)

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S = P β D V Ω .
P x = P 0 e α x .
x e = ( 1 e 2 α x p 2 α ) ,
x e = ( 1 e ( α L α R x p ) ( α L α R ) ) .

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