293 K (20 °C).
H. H. Li. Refractive index of alkaline earth halides and its wavelength and temperature derivatives. J. Phys. Chem. Ref. Data 9, 161-289 (1980) and references therein.
* Sellmeier formula is derived by critical analysis of experimental data from several sources.
* There is a misprint in the dispersion formula in the paper: "-" instead of "+" before the last term of the equation.