Dispersion of Nitrogen*

The refractivity of nitrogen gas has been measured, with high relative precision, at vacuum wavelengths from 4679 Å to 20 586 Å. The absolute value of refractivity for 5462 Å, reduced to one atmosphere at 0°C., is 2.991×10−4. A dispersion formula fitting the data well at 15°C. is 108 (n−1)= 6497.378+3 073 864.9/(144-σ2), where σ is wave number in reciprocal microns. This is compared to Svensson’s dispersion formula for air. Alternative dispersion formulas are discussed. Quantities related to dispersion are deduced: mean absorption frequency, effective total oscillator strength., dielectric constant, Verdet constant, and Rayleigh scattering coefficient.