The precise determination of refractometric parameters for atmospheric gases
The precise determination of refractometric parameters for atmospheric gases
This thesis is concerned with the precise determination of the refractive indices of gases and in particular air. The development of an automatic interferometric refractometer is described which has a measurement accuracy of ± 1 x 10^-8 in refractive index and an operating wavelength of 633 nm. The validity of the Edlen and Owens air refractive index equations have been assessed over the temperature range 10 to 30^oC and atmospheric pressure range 20 to 115 kPa using a standard composition of dry air. Both of the equations appear to be accurate to within the experimental accuracy of the measurements of ± 3.2 x 10-8. However the measurements made on moist standard air suggest that the water vapour terms in both equations are in error by -1.3 x 10-7 for fully saturated air at 20oC. Water vapour adsorption effects are shown to be a possible error mechanism for this term. The measurements on moist standard air have enabled a modified Edlen equation to be produced which has been found to accurately calculate the refractive index of atmospheric air in four geographical locations when account is taken of the levels of carbon dioxide which exceed that assumed by Edlen. The Lorenz - Lorentz equation and its adititity form have been examined for dry air and they have both been seen to be valid to within their respective experimental accuracies of about ± 3 and ± 1.5 parts in 104. In addition the refractive indices of N2, O2, A, CO2 and other atmospheric gases have also been precisely determined. (DX 84121)
University of Southampton
1988
Birch, Keith Patrick
(1988)
The precise determination of refractometric parameters for atmospheric gases.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis is concerned with the precise determination of the refractive indices of gases and in particular air. The development of an automatic interferometric refractometer is described which has a measurement accuracy of ± 1 x 10^-8 in refractive index and an operating wavelength of 633 nm. The validity of the Edlen and Owens air refractive index equations have been assessed over the temperature range 10 to 30^oC and atmospheric pressure range 20 to 115 kPa using a standard composition of dry air. Both of the equations appear to be accurate to within the experimental accuracy of the measurements of ± 3.2 x 10-8. However the measurements made on moist standard air suggest that the water vapour terms in both equations are in error by -1.3 x 10-7 for fully saturated air at 20oC. Water vapour adsorption effects are shown to be a possible error mechanism for this term. The measurements on moist standard air have enabled a modified Edlen equation to be produced which has been found to accurately calculate the refractive index of atmospheric air in four geographical locations when account is taken of the levels of carbon dioxide which exceed that assumed by Edlen. The Lorenz - Lorentz equation and its adititity form have been examined for dry air and they have both been seen to be valid to within their respective experimental accuracies of about ± 3 and ± 1.5 parts in 104. In addition the refractive indices of N2, O2, A, CO2 and other atmospheric gases have also been precisely determined. (DX 84121)
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Published date: 1988
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Local EPrints ID: 460769
URI: http://eprints.soton.ac.uk/id/eprint/460769
PURE UUID: 51444b92-d4fd-4f52-8afd-d7a76624979b
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Date deposited: 04 Jul 2022 18:29
Last modified: 04 Jul 2022 18:29
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Author:
Keith Patrick Birch
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