Abstract
Below the critical point the liquid-vapor interface of a simple fluid is characterized by a thin transition layer across which the values of density vary between the two phases. This transition layer can be described by a density profile characterized by an effective interface thickness . As the temperature approaches the critical temperature , diverges as , where . From the measurement of optical reflectivity of the liquid-vapor interface of sulfur hexafluoride, we have deduced the interface thickness and the critical index for the coexistence curve. In the temperature range we find if an error-function profile is assumed as proposed by Buff, Lovett, and Stillinger, or if the density profile proposed by Fisk and Widom is used. For both profiles is found equal to 0.333 ± 0.008. These indices, when combined with the critical index for the isothermal compressibility and for the surface tension, are used to test various scaling relations.
- Received 27 April 1973
DOI:https://doi.org/10.1103/PhysRevA.8.2065
©1973 American Physical Society