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Absolute refractometry of dry gas to ±3 parts in 109



Patrick F. Egan, Jack A. Stone Jr.


We present a method of measuring the refractive index of dry gases absolutely at 632.8 nm wavelength using a Fabry-Perot cavity with an expanded uncertainty of -9 (coverage factor k = 2. The main contribution to this uncertainty is how well vacuum-to-atmosphere compression effects (length variation) in the cavities can be corrected for. This paper describes the technique and reports reference values for the refractive index of nitrogen and argon gases at 100 kPa and 20 °C with an expanded uncertainty of -9 (coverage factor k{\I} = 2), with the largest part of this uncertainty coming from the pressure and temperature measurement.
Applied Optics


Metrology, Fabry-Perot, Refraction, Laser stabilization


Egan, P. and Stone, J. (2011), Absolute refractometry of dry gas to &#177;3 parts in 10<sup>9</sup>, Applied Optics, [online], (Accessed June 15, 2024)


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Created June 20, 2011, Updated November 10, 2018