Index of refraction, Rayleigh scattering length, and Sellmeier coefficients in solid and liquid argon and xenon

Like all the noble elements, argon and xenon are scintillators, \emph{i.e.} they produce light when exposed to radiation. Large liquid argon detectors have become widely used in low background experiments, including dark matter and neutrino research. However, the index of refraction of liquid argon at the scintillation wavelength has not been measured and current Rayleigh scattering length calculations disagree with measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce a new calculation using previously measured data in liquid and solid argon and xenon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship. As a point of validation, we compare our extrapolated index of refraction for liquid xenon against the measured value and find agreement within the uncertainties. This method results in a Rayleigh scattering length for liquid argon at the triple point of 55 $\pm$ 5 cm, a Rayleigh scattering length of 40 $\pm$ 4 cm for solid argon at the triple point, and a Rayleigh scattering length of 14 $\pm$ 1 cm for solid xenon at the triple point.