Optical response of liquid mercury

In many of the results of previous investigations, systematic differences have been observed in the directly measured reflectances of liquid Hg and those calculated from the optical constants determined by ellipsometry. We have performed a comprehensive set of experiments on liquid Hg at room temperature in order to resolve the problem of whether these discrepancies are real. A summary of some of our results have been published [Phys. Rev. B 40, 11994 (1989)]. Here we present a more detailed account of the experimental details and some new results. The spectral range of these experiments was confined to the visible spectral region. Normal-incidence reflectances of liquid Hg under vacuum and in contact with dielectric overlayers were measured. Reflectances of polarized light were measured at a photon angle of incidence of 70° for liquid Hg under vacuum. The optical constants of liquid Hg in contact with various dielectric overlayers were determined by ellipsometry and also by measuring reflectances as a function of angle of photon incidence at a MgF₂-Hg interface. The results of the direct reflectance measurements were consistent with the optical properties determined by ellipsometry. No evidence was found for transition layers on the surface of liquid Hg.