Some Properties of Small Gas Molecules Determined by Refractive Index Measurements

The dispersion of the refractive index of the gases He, Ne, Ar, H 2 , N 2 , O 2 , CH 4 , and C(CH 3 ) 4 at low densities is determined in the visible wave length range 400 nm ≦ λ ≦ 700 nm by means of scanning‐wavelength interferometry. The measurements are fitted by one‐term Kramers‐Heisenberg dispersion relations and used to calculate some macroscopic and molecular properties like mean polarizabilities, effective eigenenergies and oscillator strengths, oscillator strength sums, Verdet and related constants, Rayleigh scattering cross sections and dispersion force constants. The theoretical background as well as the significance of the different relations between refractive index and these properties is presented and discussed briefly.