Optical properties of liquid Pb and Bi between 0.6 and 3.7 eV

Optical properties of liquid Pb and Bi were determined at 341 and 285^∘{}C, respectively, for photon energies between 0.6 and 3.7 eV, with the use of an ultra-high-vacuum ellipsometer. It was found that liquid Pb exhibits absorption in excess of Drude absorption, with a structure strikingly similar to the interband absorption in solid Pb. The liquid-to-solid ratio of the interband intensity was found to be 0.22, and 11% of the total valence oscillator strength in the liquid was attributable to the interband transitions. Liquid Bi was also found to exhibit excess absorption at energies above 2.5 eV. These non-Drude behaviors of both liquids were found to be explained as a density-of-states effect by assuming the nondirect model for optical transitions in liquid metals.