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Optical n(p, T_90) measurement suite 2: H_2O and D_2O



Patrick Egan, Yuanchao Yang


A suite of measurements of refractive index n(p, T_90) is reported for gas phase ordinary water H_2O and heavy water D_2O. The methodology is optical refractive index gas metrology, operating at laser wavelength 633 nm and covering the range (293 < T_90 < 433) K and p < 2 kPa. A key output of the work is the determination of molar polarizabilities A_R = 3.7466(18) * [1 + 1.5(6) x 10^-6 (T/K - 303) ] cm^3/mol for ordinary water, and A_R = 3.7135(18) * [1 + 4.4(10) x 10^-6 (T/K - 303) ] cm^3/mol for heavy water, with the numbers in parentheses expressing standard uncertainty. For heavy water, this work appears to be only the second gas phase measurement to date. For both ordinary and heavy water, this work agrees within 0.15 % with recent ab initio theoretical results for A_R, but the comparison is affected by imperfect knowledge of dispersion. For ordinary water, the close agreement between the present work and theory suggests problems at the 2 % level in the low density limit of the reference formulation for refractivity.
International Journal of Thermophysics


Water vapor, refractometry, polarizability, thermodynamic metrology


Egan, P. and Yang, Y. (2024), Optical n(p, T_90) measurement suite 2: H_2O and D_2O, International Journal of Thermophysics, [online],, (Accessed June 25, 2024)


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Created May 28, 2024, Updated May 30, 2024