Optical constants and dispersion equations of lecithin, cholesterol, fucose, and chloroform: Measurements in vacuum-ultraviolet to visible wavelength regions

The optical constants, n and k, of solutions of lecithin, cholesterol, and fucose and of the solvent chloroform are measured for the spectral region 1348 to 6407 Å by a reflectance method. Absorption peaks are found in chloroform at about 1393 and 1631 Å and are attributed, respectively, to σ → σ electron transitions at the C-H and C-Cl bonds and an n → σ electron transition at the C-Cl bond. A procedure for the determination of the optical constants of a solute from those of the solution and solvent is developed and applied. The procedure is also applied to calculate the optical constants of a solution from those of the components. From the values of the optical constants, dispersion equation parameters and van der Waals parameters are calculated for the compounds. The static electronic polarizabilities of the substances studied are found to depend little (less than 6%) on the concentration of solution used in the measurement. Values of polarizabilities obtained agree closely with those obtained by the addition of bond polarizabilities.