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Absolute refractometry of dry gas to ±3 parts in 109
Published
Author(s)
Patrick F. Egan, Jack A. Stone Jr.
Abstract
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.
Egan, P.
and Stone, J.
(2011),
Absolute refractometry of dry gas to ±3 parts in 10<sup>9</sup>, Applied Optics, [online], https://doi.org/10.1364/AO.50.003076
(Accessed October 10, 2025)