Refractive Index of Arsenic Trisulfide

The refractive index of a sample of As2S3 was determined at three temperatures near 19°, 25°, and 31°C for selected wavelengths in the range 0.57 μ to 11.8 μ. A five term Sellmeier type dispersion equation was fitted to the averaged data reduced to 25°C; four of the constants were chosen to approximate an absorption continuum in the ultraviolet and visible while the fifth term was arbitrarily chosen as beyond the infrared absorption edge. The indexes of refraction in the visible region of two other samples were obtained for comparison.