Dispersion of Helium

The refractivity of helium computed from experimental measurements made at 15 different wavelengths by use of a corner-reflector Michelson interferometer, and computed from recent theoretical values of oscillator strength at 26 different wavelengths, is reported. The experimental measurements range from 4801 to 20586 Å. The absolute refractivity at 760 torr, 0°C, 5462.258 Å is 3.4950×10−5. A dispersion formula describing the data is (n-1)×105=1470.091/(423.98-σ2).Other dispersion formulas are discussed. The experimental and theoretical computations are compared with the experimental and theoretical work of various authors. The comparison includes computations of effective F values, absorption wavelength, dielectric constant, molecular polarizability, and Verdet constant.