The dispersion and aging effects of thin films of MgF2 and ZnS were investigated in the spectral range of 4000 A to 7500 A. The method of evaporating ZnS is reported. The index of refraction was calculated from spectrophotometric reflectance measurements at extremes of reflectance.
JOSEPH F. HALL, JR. and W. F. C. FERGUSON, "Dispersion of Zinc Sulfide and Magnesium Fluoride Films in the Visible Spectrum," J. Opt. Soc. Am. 45, 74-75 (1955)