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Applied Optics

Applied Optics


  • Vol. 41, Iss. 12 — Apr. 20, 2002
  • pp: 2292–2298

Refractive index of air: 3. The roles of CO2, H2O, and refractivity virials

Philip E. Ciddor  »View Author Affiliations

Applied Optics, Vol. 41, Issue 12, pp. 2292-2298 (2002)

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The author’s recent studies of the refractive index of air are extended, and several assumptions made therein are further examined. It is shown that the alternative dispersion equations for CO2, which are due to Edlen [Metrologia 2, 71 (1966)] and Old et al. [J. Opt. Soc. Am. 61, 89 (1971)] result in differences of less than 2 × 10-9 in the phase refractive index and less than 3 × 10-9 in the group refractive index for current and predicted concentrations of CO2. However, because the dispersion equation given by Old et al. is consistent with experimental data in the near infrared, it is preferable to the equation used by Edlen, which is valid only in the ultraviolet and the visible. The classical measurement by Barrell and Sears [Philos. Trans. R. Soc. London Ser. A 238, 1 (1939)] on the refractivity of moist air is shown to have some procedural errors in addition to the one discussed by Birch and Downs [Metrologia 30, 155 (1993)]. It is shown that for normal atmospheric conditions the higher refractivity virial coefficients related to the Lorentz-Lorenz relation are adequately incorporated into the empirically determined first refractivity virial. As a guide to users the practical limits to the calculation of the refractive index of the atmosphere that result from the uncertainties in the measurement of the various atmospheric parameters are summarized.

© 2002 Optical Society of America

OCIS Codes
(010.1290) Atmospheric and oceanic optics : Atmospheric optics
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.3940) Instrumentation, measurement, and metrology : Metrology

Original Manuscript: August 6, 2001
Revised Manuscript: November 26, 2001
Published: April 20, 2002

Philip E. Ciddor, "Refractive index of air: 3. The roles of CO2, H2O, and refractivity virials," Appl. Opt. 41, 2292-2298 (2002)

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  1. P. E. Ciddor, “Refractive index of air: new equations for the visible and the near infrared,” Appl. Opt. 35, 1566–1573 (1996). [CrossRef] [PubMed]
  2. P. E. Ciddor, R. J. Hill, “Refractive index of air: 2. Group index,” Appl. Opt. 38, 1663–1667 (1999). [CrossRef]
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  14. K. P. Birch, M. J. Downs, “The precise determination of the refractive index of air,” Rep. MOM90, (National Physical Laboratory, Teddington, Middlesex, TW11 0LW, U.K., 1988), pp. 1–35.
  15. K. P. Birch, 36 Fircroft Road, Chessington, Surrey, KT9 1RW, U.K. (personal communication, 2000).
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  21. R. J. Hill, “Infrared refractive index software, IR_N, 2000,” Environmental Research Laboratories, NOAA, 325 Broadway, Boulder, Colorado 80303-3328 (personal communication, May2000). (A limited number of copies of this software are available on compact disk from P. E. Ciddor or from J.M.Rueger@unsw.edu.au).
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  24. M. J. Kenny, C. J. Walsh, A. J. Leistner, K. Fen, W. J. Giardini, L. S. Wielunski, B. R. Ward, “Determination of the Avogadro constant from precision density measurements on a silicon sphere,” in Proceedings of the Conference on Precision Electromagnetic Measurements, J. Hunter, L. Johnson, eds. (Institute of Electrical and Electronic Engineers, Piscataway, N.J., 2000), pp. 184–185.

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